illustrated guide to home forensic science experiments and also explain forensic science home study courses
OliverFinch,France,Teacher
Published Date:15-07-2017
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Laboratory
1
Safety
First things first. This is a short chapter, but a very important one. Many of the lab sessions
described in this book use chemicals, such as strong acids and bases, that are dangerous
if handled improperly. Some lab sessions use open flame or other heat sources, and many
use glassware. To state the obvious, you can get hurt working in a lab. Fortunately, there are
steps you can take to minimize or eliminate hazards.
If you remember one thing from this chapter, remember this: If there is even the slightest
chance that you will be exposed to any hazardous chemical, always wear chemical
splash goggles, gloves, and protective clothing. We follow this advice ourselves, without
exception.
Most injuries that occur in student labs are minor and easily
DENNIS HILLIARD COMMENTS
avoidable. Among the most common are nicks from broken or
Whenever you are working with any chemicals, glassware,
chipped glassware and minor burns. Serious injuries are very
and/or biological material, always wear chemical splash
rare. When they do occur, it’s nearly always because someone
goggles, gloves, and protective clothing. Protective
did something incredibly stupid, such as using a flammable
clothing works two ways: it protects the analyst from
solvent near an open flame or absentmindedly taking a swig
chemical, sharps, and biological hazards associated with
from a beaker full of a toxic liquid. (That’s why one of the rules of
evidence collection and processing; and it protects from
laboratory safety is never to smoke, drink, or eat in the lab.)
contamination of the evidence by the collector/analyst.
The primary goal of laboratory safety rules is to prevent injuries.
Knowing and following the rules minimizes the likelihood of
Although working in any lab has its dangers, so does driving a accidents and helps to ensure that any accidents that do occur
car. And, just as you must remain constantly alert while driving, will be minor ones.
you must remain constantly alert while working in a lab. But
it’s also important to keep things in perspective. More serious The following are the laboratory safety rules we recommend:
injuries occur every year among a few hundred thousand
high school football players than have ever occurred in total Prepare properly
among millions upon millions of student scientists in the 200-
year history of student labs. Statistically, students are much, • All laboratory activities must be supervised by a
much safer working in a home or school lab than they are out responsible adult.
skateboarding or riding bicycles.
Chapter 1 : Laboratory Safety 1Direct adult supervision is mandatory for all of the activities The MSDS is a concise document that lists the specific
in this book. This adult must review each activity before characteristics and hazards of a chemical. Always read the
it is started, understand the potential dangers of that MSDS for every chemical that is to be used in a lab session.
activity and the steps required to minimize or eliminate If an MSDS was not supplied with the chemical, locate one
those dangers, and be present during the activity from on the Internet. For example, before you use lead nitrate in
start to finish. Although the adult is ultimately responsible an experiment, do a Google search using the search terms
for safety, students must also understand the potential “lead nitrate” and “MSDS”.
dangers and the procedures that should be used to
minimize risk. • Organize your work area.
• Familiarize yourself with safety procedures and equipment. Keep your lab bench and other work areas clean and
uncluttered, before, during, and after laboratory sessions.
Think about how to respond to accidents before they Every laboratory session should begin and end with your
happen. Have a fire extinguisher and first-aid kit readily glassware, chemicals, and laboratory equipment clean and
available and a telephone nearby in case you need stored properly.
to summon assistance. Know and practice first-aid
procedures, particularly those required to deal with burns Dress properly
and cuts. If you have a cell phone, keep it with you while
you’re working in the lab. • Wear approved eye protection at all times.
One of the most important safety items in any lab is Everyone present in the lab must at all times wear splash
the cold water faucet. If you burn yourself, immediately goggles that comply with the ANSI Z87.1 standard.
(seconds count) flood the burned area with cold tap water Standard eyeglasses or shop goggles do not provide
for several minutes to minimize the damage done by the adequate protection, because they are not designed to
burn. If you spill a chemical on yourself, immediately rinse prevent splashed liquids from getting into your eyes.
the chemical off with cold tap water, and keep rinsing for Eyeglasses may be worn under the goggles, but contact
several minutes. Ideally, every lab should have an eyewash lenses are not permitted in the lab. (Corrosive chemicals
station, but most home labs do not. If you do not have an can be trapped between a contact lens and your eye,
eyewash station and you get any chemical in your eyes, making it difficult to flush the corrosive chemical away.)
immediately turn the cold tap on full and flood your eyes
until help arrives. • Wear protective gloves and clothing.
Never allow laboratory chemicals to contact your bare
skin. When you handle chemicals, particularly corrosive
WARNING
or toxic chemicals or those that can be absorbed through
Everyone rightly treats strong acids with great respect, but
the skin, wear gloves of latex, nitrile, vinyl, or another
many students handle strong bases casually. That’s a very
chemical-resistant material. We recommend disposable
dangerous practice. Strong bases, such as solutions of
nitrile gloves, which you can purchase at Costco, Walmart,
sodium hydroxide, can blind you in literally seconds. Treat
or any drugstore. We are comfortable using disposable
every chemical as potentially hazardous, and always wear
nitrile gloves for handling any of the chemicals used in
splash goggles.
this book. If you want to be extra cautious when handling
corrosive and/or toxic chemicals, either double-glove with
disposable nitrile gloves or wear heavier gloves, such as the
Keep a large container of baking soda (sodium thick “rubber” gloves sold by lab supply vendors and in the
bicarbonate) on hand to deal with acid or base spills. supermarket for household use.
Baking soda neutralizes either type of spill. We keep a
12-pound bag from Costco on hand for this purpose. Wear long pants, a long-sleeve shirt, and leather shoes or
boots that fully cover your feet (NO sandals). Avoid loose
• Always read the Material Safety Data Sheet (MSDS) for sleeves. To protect yourself and your clothing, wear a
every chemical you will use in a laboratory session. lab coat or a lab apron made of vinyl or another resistant
material. Wear a disposable respirator mask if you handle
chemicals that are toxic by inhalation.
2 DIY Science: Illustrated Guide to Home Forensic Science ExperimentsAvoid laboratory hazards Don’t Do Stupid Things
• Avoid chemical hazards. • Never eat, drink, or smoke in the laboratory.
Never taste any laboratory chemical or sniff it directly. All laboratory chemicals should be considered toxic by
(Use your hand to waft the odor toward your nose.) Never ingestion, and the best way to avoid ingesting chemicals is
use your mouth to fill a pipette. When you heat a test tube to keep your mouth closed. Eating or drinking (even water)
or flask, make sure the mouth points in a safe direction. in the lab is very risky behavior. A moment’s inattention can
Always use a boiling chip or stirring rod to prevent liquids have tragic results. Smoking violates two major lab safety
from boiling over and being ejected from the container. rules: putting anything in your mouth is a major no-no, as is
Never carry open containers of chemicals around the carrying an open flame around the lab.
lab. Always dilute strong acids and bases by adding the
concentrated solution or solid chemical to water slowly • Never work alone in the laboratory.
and with stirring. Doing the converse can cause the liquid
to boil violently and be ejected from the container. Use the No one—adult or student—should ever work alone in the
smallest quantities of chemicals that will accomplish your laboratory. Even if the experimenter is adult, there must at
goal. In particular, the first time you run a reaction, do so least be another adult within earshot who is able to respond
on a small scale. If a reaction is unexpectedly vigorous, it’s quickly in an emergency.
better if it happens with 1 mL of chemicals in a spot plate
than 500 mL in a large beaker. • Never horse around.
• Avoid fire hazards. A lab isn’t the place for practical jokes or acting out, nor for
that matter for catching up on gossip or talking about last
Never handle flammable liquids or gases in an area where night’s ball game. When you’re in the lab, you should have
an open flame or sparks might ignite them. Extinguish your mind on lab work, period.
burners as soon as you finish using them. Do not refuel a
burner until it has cooled completely. If you have long hair, • Never combine chemicals arbitrarily.
tie it back or tuck it up under a cap, particularly if you are
working near an open flame. Combining chemicals arbitrarily is among the most
frequent causes of serious accidents in home labs. Some
• Avoid glassware hazards. people seem compelled to mix chemicals more or less
randomly, just to see what happens. Sometimes they get
Assume all glassware is hot until you are certain otherwise. more than they bargained for.
Examine all glassware before you use it, and particularly
before you heat it. Discard any glassware that is cracked, Laboratory safety is mainly a matter of common sense. Think
chipped, or otherwise damaged. Learn the proper about what you’re about to do before you do it. Work carefully.
technique for cutting and shaping glass tubing, and make Deal with minor problems before they become major problems.
sure to fire-polish all sharp ends. Keep safety constantly in mind, and chances are any problems
you have will be very minor ones.
Chapter 1 : Laboratory Safety 3Equipping Your Forensics
2
Laboratory
To do a serious study of forensic science lab work, you’ll need some specialized equipment
and chemicals. Fortunately, it needn’t be expensive to acquire the items you need. You may
already have some of those items, such as a microscope purchased for a biology course or
a balance and other lab equipment purchased for a chemistry course.
To make matters as easy and inexpensive as possible, as we wrote this book we designed
a custom lab kit to go with it (http//:www.thehomescientist.com/kits/FK01/fk01-main
.html). With the exception of readily available materials, major items (such as a microscope
and balance), and some optional items, this kit includes the specialized equipment and
chemicals you need to complete the lab sessions in this book. Of course, you don’t have to
buy the kit to use this book. We provide full details of what’s needed for each lab session,
and all of those materials can be obtained locally or purchased individually from numerous
online lab supply vendors and law-enforcement forensic supply vendors.
Optical EquipmEnt
The iconic image of Sherlock Holmes has him smoking a pipe, wearing a deerstalker cap, and
examining evidence with his magnifying glass. The pipe and cap are optional but, as Holmes knew
well, optical equipment is essential for successful forensic investigations. Like Holmes, we’ll use a
variety of optical aids in our investigations, all of which are described in the following sections.
the crime scene as it was first encountered, with both overall
IMAGING EqUIPMENT
images to show the crime scene in context and close-up images
One of the fundamental principles of crime scene management to show details of objects of particular evidentiary value.
is that everything possible should be recorded in situ
photographically. Once an object has been moved, the scene Photography is also used extensively for recording specimens
is permanently altered. The primary goal of crime scene that have been recovered from the crime scene and transported
photography is therefore to preserve a permanent record of to the forensics laboratory. Such images provide a permanent
record of specimens as they appeared when they were received
Chapter 2 : Equipping Your Forensics Laboratory 5by the lab, and are particularly useful for situations in which Digital cameras soon achieved resolution nearly as good as the
subsequent testing may alter the appearance of the evidence, best available film cameras—and in some cases, better—which
perhaps permanently. answered the first objection. And, as it turned out, sophisticated
digital image analysis algorithms can detect changes to digital
images, answering the second objection, as well.
CAMERA (OPTIONAL)
Forensic technicians have routinely photographed crime scenes
since the last quarter of the 19th century. At that time, the
DENNIS HILLIARD COMMENTS
best cameras available were large, bulky, and used glass plate
Despite their relatively low image quality, camcorders
emulsions that for anything other than full daylight required
were formerly widely used to record crime scene video.
long exposure times or flash exposures that scattered unburned
With the use of digital still cameras, crime scene video has
flash powder and ashes all over crime scenes. As camera
fallen out of favor. The digital camera is used to document
technology improved, so too did the quality and quantity of
the entire scene and photos can be stitched together in
crime scene images. Today, most crime scene photographers a computer program such as Adobe Photoshop to give
panoramic views.
use both standard digital SLRs—film cameras are seldom used
any longer, other than in special situations—and specialized
cameras that capture images in the infrared or ultraviolet
portions of the spectrum. Although you won’t be photographing any crime scenes
for the lab sessions in this book, a camera is also useful for
Because any camera inherently distorts reality by representing recording images of specimens for your lab notebook, shooting
three-dimensional scenes in two dimensions and by rendering photomicrographs (images through the microscope), and so
colors and contrasts imperfectly, crime scene photographers on. If you don’t have a suitable camera, you can make sketches,
take great care to minimize any such effects their equipment instead.
may impose on the final images and to record the pertinent
data about each image. For example, because the focal length
of a lens affects perspective, back when film cameras were DENNIS HILLIARD COMMENTS
in common use, many crime scene photographers used
Sketches are often a part of the analyst’s notes and are
only fixed-focal length lenses or, alternatively, recorded the
required in accredited laboratories, because notes are
focal length used for each image. That’s seldom a problem
subject to review and photos are not always able to be
nowadays, because nearly all digital cameras record such data taken of some evidence or are difficult to take through a
microscope.
automatically and store it with the image file. Crime scene
photographers also use grids to show the distances and angular
relationships among objects in the image. Similarly, where
image scale is not obvious, crime scene photographers take If possible, use a digital camera with a macro feature, ideally one
great care to make image scale clear within the image itself, for that permits imaging to at least a 1:3 scale (1:3 means the image
example, by including a section of a ruler next to an object in an on the sensor is a third the size of the actual object), and 1:2 or
image. 1:1 is better. A point-and-shoot digital camera is acceptable; a
digital SLR is preferable. Although some standard “kit” zoom
In the last few years, digital cameras have come to dominate lenses supplied with digital SLRs allow focusing down to a 1:3 or
crime scene photography. Digital images are immediately closer ratio, these lenses do not provide the best image quality
accessible, much less expensive than film images, and much for extreme close-ups. A macro lens—one optimized for best
easier to store, copy, search, and transfer. The main early image quality at very short distances—is the best choice for
impediments to widespread adoption of digital imaging for macro shots. We use Pentax K100D Super and K-r digital SLRs
forensics were the relatively low resolution of early digital with a Pentax 50mm macro lens.
cameras and the perception that digital images could be altered
easily and undetectably, making them useless as evidence.
6 DIY Science: Illustrated Guide to Home Forensic Science ExperimentsBecause an on-camera flash unit provides flat lighting other
than at very close focusing distances, it’s also helpful to have a
A camera records an image from a fixed sensor (lens)
small slave flash unit to provide low-angle or cross lighting for
position, which means that different objects within the
contrast when photographing small specimens. We use a 25 field of view are imaged at slightly different angles and
distances, even if the object is flat. For example, if you use
Vivitar DF120, which is triggered by the main flash.
a camera to shoot an image of a document, the camera
lens is slightly closer to the center of the document than
SCANNER (OPTIONAL)
to the corners, introducing some distortion. We think
nothing of this, because that’s also how our eyes work.
One relatively recent development has been the use of ordinary
A scanner, conversely, images objects with a moving
PC flat-bed scanners for recording high-resolution images of flat
sensor. Each tiny part of the image is made with the
specimens, usually in the lab but sometimes at the crime scene.
sensor effectively in contact with the subject, so there
One major advantage of using a scanner is that the images are
is essentially no distortion of flat objects, such as
automatically calibrated, with the resolution stored in the image
documents, surfaces, or clothing specimens. It is because
file header. You can open an image file with Photoshop or a
scanner images have nearly zero distortion that accurate
similar graphics program and perform direct measurements on
direct measurements may be made from them.
the image. Alternately, you can count pixels and simply convert
pixels to millimeters or inches using a spreadsheet. Because
typical scanners record images at 2,400 to 9,600 dpi (dots per
MAGNIFIER (REquIRED )
inch) or higher, such measurements are accurate and precise.
Figure 2-1 shows a small fabric tear imaged at 3,200 dpi using One of the most useful items in any forensic kit is a magnifier
an inexpensive Epson scanner. that provides moderate magnification, something in the range
of 5X to 15X. A magnifier provides a close-up view of small
Figure 2-1: A fabric tear imaged at 3,200 dpi using a scanner objects, fingerprints, and other small but significant evidence.
The FK01 Forensic Science Kit includes an inexpensive
folding magnifier, but if you have a better magnifier or
loupe, by all means use it.
Sherlock Holmes used a simple magnifying glass, but there are
better tools available today. The best choice is a photographer’s
loupe with a transparent base, such as the 5X Viewcraft Lupe
shown in Figure 2-2.
With some scanners, you can remove the lid, invert the scanner
over (for example) a stain on the floor, and record an image
directly. Results are often better than camera images because
the scanner provides a flat, even light, eliminating the problems
with hot spots and reflections that are common with an on-
camera flash.
Chapter 2 : Equipping Your Forensics Laboratory 7Figure 2-2: A 5X Viewcraft Lupe A stand magnifier, preferably illuminated, is useful for examining
objects while keeping both hands free. The model shown in
Figure 2-4 provides 2X magnification overall and has a smaller
embedded lens that provides 4X magnification of small parts of
the object. Magnifiers like this one are available from stores and
catalogs that serve the needs of the elderly.
Figure 2-4: A stand magnifier allows you to work with both
hands free
A loupe with a built-in scale or reticle allows you to determine
the size of objects directly, as shown in Figure 2-3. (A scale
appears alongside the object in the field of view, while a reticle
is superimposed optically on the image.) A basic loupe costs 5
to 15 and can be purchased from any vendor of photography
supplies. High-quality loupes from German and Japanese
makers are considerably more expensive. Some loupes have
built-in illuminators, but most do not. Even if your loupe is
illuminated, but particularly if it is not, add a small flashlight to
MICROSCOPE (REqUIRED )
your portable forensics kit. We use a two-AA model with a white
LED bulb, although many forensics technicians prefer to use a Microscopes take over where magnifiers leave off. Typical
flashlight with an incandescent bulb because it renders colors magnifiers enlarge an object by 5X to 15X, while microscopes
more accurately. enlarge objects from about 10X to 1000X or more. Modern
forensics labs use many different kinds of microscopes,
including electron microscopes, microscopes designed to
Figure 2-3: A loupe with a scale or reticle allows you to measure work with polarized or UV light, and comparison microscopes
objects directly that allow viewing two samples side by side in the same field of
view. Such specialized microscopes are much too expensive
for a basic forensics lab, but all of the lab sessions in this book
that require a microscope can be completed with a standard
compound microscope. A 40/100/400X model will suffice
for all but the lab sessions that require observing diatoms
and pollen; for those, a 40/100/400/1000X model is a better
choice. If at all possible, use a microscope with a mechanical
stage. Many microscopes include an ocular micrometer/reticle
as a standard or optional feature. This is worth having, because
it allows you to determine the actual sizes of objects you’re
viewing through the microscope.
8 DIY Science: Illustrated Guide to Home Forensic Science Experimentspermanently, you’ll need mounting fluid. You can buy
special permanent mounting fluids such as Permount or
For detailed information about choosing and buying
a microscope, see Illustrated Guide to Home Biology Melt-Mount, but a drop of colorless nail polish (we use
Experiments.
Sally Hansen Hard as Nails) works about as well. The FK01
Forensic Science Kit includes glycerol and olive oil, both of
which are suitable for temporary wet mounts.
MICROSCOPE ACCESSORIES
Slide storage
In addition to the compound microscope itself, you’ll need a Most science supply vendors carry a variety of slide
modest selection of supplies and accessories. Most laboratory storage boxes in plastic and wood as well as slide folders. If
supply vendors offer starter kits that contain many of these you intend to permanently mount specimens, buy boxes or
items. folders as necessary to store your slides.
Slides Immersion oil
You’ll need a reasonable number of standard (25×75 mm or If your compound microscope has an oil-immersion
1×3") microscope slides. Buy a box of 72; you’ll use a lot of objective (usually the 100X objective), you’ll need
slides. Avoid the cheapest slides, which may be fragile and immersion oil. If your microscope doesn’t have an oil-
have sharp edges. You’ll also need a few concavity slides immersion objective or if you don’t plan to use high
(also called well slides). These are useful for containing magnification, you can do without immersion oil.
small specimens and performing micro-procedures on
them. Buy deep-cavity slides, which are about three times Cleaning kit
the thickness of standard slides (3 mm versus 1 mm). The You’ll need to clean the ocular and objective lenses of your
deep-cavity models are harder to find and more expensive microscope periodically. If you use immersion oil, you
than standard well slides, but they’re also much more should clean the immersion objective each time you use it.
useful. The FK01 Forensic Science Kit includes a box of 72 Science supply vendors carry cleaning kits that include a
flat slides and a box of 12 deep-cavity slides. blower, brush, lens-cleaning tissue and fluid, and so on.
Coverslips Dust cover or storage case
Buy a half-ounce or one-ounce box of standard 18×18 mm One of the most important and frequently overlooked
to 24×24 mm square glass coverslips. 1.5 coverslips are accessories is a dust cover or storage case for the
the ideal thickness for most standard microscopes, but microscope. Always keep your microscope covered when
they’re relatively difficult to find. 2 coverslips are suitable you are not using it to protect it from dust and damage. If
for most microscopes. Buy the very thin 1 coverslips you don’t have a cover or case, a kitchen trash bag makes
only if your microscope requires them. The FK01 Forensic an adequate substitute
Science Kit includes a box of standard coverslips.
PHOTOMICROGRAPHY EquIPMENT (OPTIONAL)
Photomicrography is the process of recording images through
Avoid all plastic slides and coverslips, which are grossly
a microscope. (Microphotography, conversely, is the process of
inferior optically to glass models. The one exception is the
lab session on doing cross sections of fibers, for which making very tiny photographs, such as the microdots formerly
you’ll need at least one plastic slide.
used by spies.) Using a camera to record the specimens you
observe with your microscope is a very useful adjunct to
narrative descriptions of your observations. Expert forensic
Mounting fluids witnesses often use photomicrographs in court to supplement
For routine use, you can simply make a temporary wet their verbal testimony.
mount by placing a drop of water, glycerol, or vegetable
oil on the specimen and then placing a coverslip on top
of the specimen, but if you want to mount specimens
Chapter 2 : Equipping Your Forensics Laboratory 9The ideal setup for photomicrography in a basic forensics lab
SPECTROMETER (OPTIONAL)
is a dual-head microscope with a digital SLR mounted to the
vertical head by means of a T-ring and microscope adapter (see Professional forensics labs use a variety of spectrometers
Figure 2-5). Such adapters are available from camera stores, and spectrophotometers to analyze unknown substances by
Edmund Optics (http//:www.edmundoptics.com), and other examining the light they emit or absorb at specific wavelengths.
vendors. We used the Edmund Microscope Adapter (41100) Technically, a spectrometer may cover any range of wave-
and Pentax K100D Super and K-r digital SLRs with a K-mount lengths, visible and/or invisible, while a spectrophotometer
T-ring adapter to shoot many of the photomicrographs in this is limited to visible wavelengths, but spectrophotometers are
book. Similar microscope adapters are available for specific often referred to by the more inclusive (and shorter) term as
point-and-shoot digital camera models. spectrometers.
Broadly speaking, there are two classes of spectrometers.
Figure 2-5: A DSLR coupled to a microscope with a T-ring and
microscope adapter An absorption spectrometer measures how much light at
specific wavelengths is absorbed by a sample in liquid or
gaseous form. For example, a copper sulfate solution appears
blue because it selectively absorbs yellow wavelengths strongly
but is nearly transparent to blue wavelengths. Observing
the absorption spectrogram allows a scientist to identify the
compound as copper sulfate and determine its concentration.
Similarly, an atomic absorption spectrometer can be used to
identify the specific chemical elements present in an unknown
gaseous sample because each element absorbs light at specific
wavelengths characteristic to that element.
An emission spectrometer measures the light emitted by
an unknown sample that has been vaporized and heated to
incandescence. Just as each element when in an unexcited
state absorbs light at specific wavelengths, each chemical
element when in an excited state emits light at those same
wavelengths. For example, Figure 2-6 shows the line emission
spectrum of a compact fluorescent lamp, showing strong
emission lines for mercury.
Figure 2-6: The spectrum of a compact fluorescent lamp, showing
Even if you don’t have a dual-head microscope or a camera strong mercury lines (image courtesy Rob Brown)
adapter, it’s possible with patience and trial-and-error to shoot
usable photomicrographs merely by setting a point-and-
shoot digital camera to macro mode and holding it up to the
microscope eyepiece. If you attempt this method, you may
get better results if you use a short length of cardboard or
plastic tube between the eyepiece and the camera lens to block
extraneous light and make alignment easier.
10 DIY Science: Illustrated Guide to Home Forensic Science Experimentsnonetheless. We’ll use one of these spectrophotometers in
toxicology and soil analysis labs to detect barium and other
ABOuT FIGuRE 2-6
heavy metals.
We had little luck in shooting our own images of emission
spectra, so we asked Rob Brown (http//:home.comcast.
net/emcculloch-brown/astro/spectrostar.html), who
MASS SPEC
created the image shown, for permission to use one of
his images, which he kindly granted. In fact, Rob shot a
Despite its name, the mass spectrometer, another
new image for us, and included these comments when he
instrument used in forensics labs, is used to separate ions
emailed the image to me.
by mass, and so is not a spectrometer at all in the usual
sense of the word.
“The calibration is a little off. The strong green line should
line up with 546 nm, but it’s a little short of 545 nm.
The camera does not do the image justice. The colors are
very compressed due to the color filters in the camera
uLTRAvIOLET LIGHT SOuRCE ( OPTIONAL)
detector. Notice the lack of yellow (575 nm), cyan (490 nm),
Ultraviolet (UV) is electromagnetic radiation at wavelengths
and violet (400 nm). Even the orange looks muddy. I can
see visually lines at 710, 705, 685, 656, 645, and 400 too short to be visible to the human eye. UV wavelengths range
nanometers. The camera can’t.”
from 400 nanometers (nm), just beyond visible violet, down to
1 nm, beyond which lies the class of light called X-rays. Forensic
scientists use UV light in the near UV range—400 nm down to
Figure 2-6 was made by using the Project Star Spectrometer 200 nm—for many purposes, including detecting blood at crime
shown in Figure 2-7. This assembled, calibrated plastic version scenes, revealing alterations in questioned documents, and
sells for 40. examining chromatograms of colorless compounds such as
drugs and poisons.
Figure 2-7: The Project Star Spectrometer, an inexpensive
spectrophotometer The near UV range is further divided into the UVA (400 nm to
320 nm), UVB (320 nm to 280 nm), and UVC (280 nm to 200
nm) ranges. UVA light, also called long-wave UV or blacklight,
has relatively low energy and is therefore safe to work with.
We’ll use UVA light in several lab sessions in this book. UVB
and particularly UVC light has higher energy and is therefore
dangerous to work with, requiring special protective goggles
and clothing to prevent damage to eyes and skin. Because UVB
and UVC light sources are also considerably more expensive
than UVA light sources, we decided to limit the use of UV light in
these lab sessions to UVA.
UVA light sources are sold in toy and novelty shops as “black
light” lamps. Battery-powered portable UVA lights, often
described as “long-wave UV” lights, are sold by laboratory
supply vendors for as little as 10. If you already have a portable
Although they look like toys and are priced accordingly, fluorescent light such as a camping lantern, you can simply
these inexpensive spectrophotometers are serious scientific replace the standard fluorescent tube with a BLB (blacklight
instruments. Obviously, they are not as sensitive or as accurate blue) fluorescent tube of the correct size and wattage. Figure
as professional models that sell for a thousand to ten thousand 2-8 shows a typical 10 battery-powered “black light” that is
times the price, but they can be used to do real science suitable for the lab sessions in this book.
Chapter 2 : Equipping Your Forensics Laboratory 11Figure 2-8: A typical 10 battery-powered UVA “black light” Another option is an ultraviolet LED flashlight. Typical pocket
models use three AAA cells to drive an array of six to nine UV
LEDs, providing bright illumination at 395 nm. These flashlights
are widely available from online vendors for 5 to 10. We’ve
come to prefer UV LED flashlights because they provide a
relatively tight, intense beam of UV and because battery life is
much better than the tube-based units. Although none of the
lab sessions in this book requires a UV light source, having one
available is useful for several lab sessions.
Table 2-1 lists the optical equipment we recommend. Items
flagged in the FK01 column are included in the FK01 Forensic
Science Kit.
Table 2-1: Recommended optical equipment
Item FK01 Sources
Camera with macro capability (optional)○ Local/on-line vendors
Magnifier● Local/on-line vendors
○
Microscope (ocular micrometer/reticle recommended) Lab supply vendors
○
Microscope adapter for camera (optional) Camera/microscope vendors
○
Microscope cleaning kit Lab supply vendors
○
Microscope cover Microscope vendor
●
Microscope coverslips, box Lab supply vendors
○
Microscope immersion oil (optional) Lab supply vendors
●
Microscope slides, flat, box of 72 Lab supply vendors
●
Microscope slides, deep-cavity, box of 12 Lab supply vendors
○
Mounting fluid for permanent mounts (optional) Lab supply vendors, drugstores
●
Mounting fluids for temporary mounts drugstores, supermarkets
○
Scanner with software (optional) Local/online vendors
○
Spectrometer (optional) See text
○
Ultraviolet light source See text
12 DIY Science: Illustrated Guide to Home Forensic Science Experimentslaboratory Equipment
In designing the lab sessions for this book, we made every effort to keep equipment requirements
as modest as possible. With few exceptions—mainly optional items and expensive items such as
a microscope—the FK01 Forensic Science Kit includes the specialty equipment and chemicals
needed to do the lab sessions.
Most of the lab sessions in this book use microscale techniques. teardown, cleanup, and storage faster and easier, and also
These techniques are in accord with real forensic practices, minimizes disposal issues.
which usually (not always) operate on very small samples, often
as small as a single hair or a few milligrams of a questioned The following sections list and describe the equipment needed
specimen. Microscale experiments also have the advantage to complete the laboratory sessions in this book. Many of the
of using smaller and less expensive equipment and requiring items you’ll need are common household items or things that
smaller quantities of expensive chemicals. That makes setup, are readily available locally, such as the following:
Aluminum foil Ovens (standard and microwave)
Bags, plastic zip (several quart/liter and one or two gallon) Paper (white copy and bond; black)
Bottles, storage (250 and 500 mL, 1 and 2 L soft drink bottles) Paper towels
Butane lighter P en, permanent marking, ultra-fine point
(Sharpie or similar)
Cotton balls (real cotton) Pencil
Cotton swabs Refrigerator/freezer
Cups, foam, 500 mL/pint Scissors
Hair dryer (optional) Tape, masking
Hammer Tape, transparent, wide (packing tape or similar)
Nickel (US coin) Toothpicks, plastic
Newspapers or brown paper bags
In addition, you’ll need the following items:
WARNING
Goggles
Safety glasses or impact goggles are not sufficient to
All lab sessions that involve handling chemicals require
protect your eyes against chemical splashes. You need
goggles that are designed to prevent liquids from
chemical splash goggles, which are vented by cap vents
penetrating the goggles and getting into your eyes. You rather than holes. Figure 2-9 shows a set of impact goggles
on the left and proper chemical splash goggles on the right.
can purchase chemical splash goggles from any lab supply
vendor.
Chapter 2 : Equipping Your Forensics Laboratory 13Figure 2-9: Impact goggles (left) and chemical splash goggles Centrifuge tubes, 1.5 mL, 15 mL, and 50 mL
Polypropylene centrifuge tubes have numerous uses:
everything from storing specimens to holding solutions
to acting as small reaction vessels to developing
chromatography strips. The FK01 Forensic Science Kit
includes fifteen 1.5 mL tubes with snap caps and six each of
the 15 mL and 50 mL tubes with screw-on caps. If you don’t
have the kit, you can purchase these tubes from most lab
supply vendors, or simply substitute suitable small glass or
plastic containers.
Chromatography paper
Chromatography paper is used in several lab sessions.
You can purchase chromatography paper from lab supply
vendors in letter-size or larger sheets or as pre-cut strips.
If you don’t have the FK01 kit, or if you need additional
Balance chromatography paper, you can substitute strips cut from
A balance is required for Lab Sessions I-2, Examine the filter paper or bleached white coffee filters.
Physical Characteristics of Soil, and III-1, Determine
Densities of Glass and Plastic Specimens, and optional Dissection tools
but recommended for several other lab sessions. Suitable Some of the lab sessions involve manipulating tiny
pocket electronic balances are available from lab supplies specimens such as a single hair or fiber. The FK01 Forensic
vendors for as little as 25. Look for a model with Science Kit includes bent and straight dissecting needles
centigram (0.01 gram) resolution and a capacity of 100 and forceps. If you don’t have the kit, you can buy these
to 200 grams. Such a balance is also useful for the other items individually or as part of a dissecting kit from any lab
sciences, including biology, chemistry, and physics. supply vendor, or you can substitute household tweezers
and large sewing needles.
Beakers, 100 mL and 250 mL
Many lab sessions require making up solutions and other Digital voice recorder
activities for which 100 mL and 250 mL polypropylene Although it is optional, a digital voice recorder is extremely
beakers are useful. You can can purchase suitable beakers useful for taking voice notes hands-free during procedures.
from any lab supplies vendor, or substitute measuring cups We use an old Olympus WS-100 digital voice recorder,
or similar containers. which hangs around Robert’s neck on a lanyard, but you
can substitute a cell phone, MP3 player, or other device
Bottle, sprayer that has a digital voice recorder function.
Some lab sessions require misting a surface with a
particular reagent. The FK01 Forensic Science Kit includes Dishes, drying
a suitable sprayer bottle. If you don’t have the kit, you can Two of the lab sessions in the soil analysis group require
buy small “fingertip sprayer bottles” at most drugstores for drying soil specimens in the oven. You can use any oven-
a dollar or so. safe flat containers—saucers, oven dishes, and so on—or
even boats made from aluminum foil. Disposable aluminum
Burner, gas pie plates, which are used in another lab session, are also
Lab I-5, Examine the Spectroscopic Characteristics of an excellent choice.
Soil, requires a gas burner of some sort. Hardware store
propane torches are suitable, as are the small gas torches Filters, plane-polarizing
sold for soldering and other hobby purposes. In a pinch, Two of the lab sessions involved examining specimens
you can substitute a natural gas kitchen stove burner. by polarized light. For those sessions, you’ll need a pair
of plane-polarizing filters, which are included in the FK01
14 DIY Science: Illustrated Guide to Home Forensic Science ExperimentsForensic Science Kit. If you don’t have the kit, you can the chemicals you’ll be using. It’s important to use gloves
purchase these filters from most lab supply vendors, or that fit your hands properly. If the gloves are too small,
you can substitute a pair of plane-polarizing camera filters. they stretch excessively and are more likely to develop
(Although we haven’t tested it, you may also be able to pinholes or even tear. If they’re too large, it’s more difficult
substitute polarizing sun glasses.) to manipulate small items while wearing them.
Fingerprint brush
The lab session on dusting for fingerprints requires a
When you’re working with particularly corrosive
suitable brush, which is included in the FK01 Forensic
chemicals—such as diphenylamine reagent, Mandelin
Science Kit. If you don’t have the kit, you can substitute
reagent, and Marquis reagent—you may wish to use more
a small artist’s paintbrush, a makeup brush, or a similar
protection than a single thin layer of latex or nitrile. In
soft-bristled brush, ideally camelhair. In a pinch, you
that case, either double-glove with exam gloves or wear
can substitute a feather. (Actually, a few professional heavier gloves, such as the heavy “rubber” gloves sold in
supermarkets for household use.
fingerprint technicians prefer a feather to any brush.) The
size of the brush is a matter of personal preference. Some
professional fingerprint technicians prefer a very small
brush, while others prefer a brush with bristles 2 cm or Graduated cylinders, 10 mL and 100 mL
more in diameter. Many lab sessions require measuring solutions
accurately. You’ll need both 10 mL and 100 mL graduated
Fuming chambers cylinders, either glass or polypropylene. Glass cylinders
Two lab sessions in the fingerprinting group require fuming are transparent, but are easily broken. Polypropylene
chambers, one for iodine and the other for superglue. cylinders are translucent, but are unbreakable and have
The required sizes of both depend on the sizes of your no meniscus. Which you use is personal preference. The
specimens. For the superglue fuming chamber, we FK01 Forensic Science Kit includes 10 mL and 100 mL
used a disposable plastic one-quart Gladware kitchen polypropylene cylinders. If you don’t have the kit, you can
container with a snap lid, which is also suitable for iodine- purchase graduated cylinders from any lab supply vendor.
fuming small specimens. If you are iodine-fuming larger
specimens, use a one-gallon zip lock plastic bag. Inoculating loop
The lab session on spectroscopic analysis of soil requires
an inoculating loop, which the FK01 Forensic Science Kit
includes. If you don’t have the kit, you can purchase an
Any chamber you use for superglue fuming will have a
inoculating loop from any lab supply vendor, or you can
cloudy layer of superglue covering all its interior surfaces,
substitute a large sewing needle with the tip embedded in
so use something disposable. Iodine stains can be
removed with a solution made by dissolving a vitamin C a wooden dowel or pencil. If you don’t intend to do that lab
tablet in a few milliliters of tap water.
session, you don’t need the loop. If you don’t have the kit,
inoculating loops are available from any lab supply vendor.
Gloves Leads, alligator clip
Wear chemical-resistant gloves at all times while working In Lab Session XI-4, DNA Analysis by Gel Electrophoresis,
with chemicals and/or specimens. The purpose of the we construct and use a DNA gel electrophoresis apparatus.
gloves is two-fold: to protect you from chemicals, and To construct that apparatus, you’ll need a pair of alligator
to protect the specimens from being contaminated by clip leads, which are included in the FK01 Forensic Science
oils and other substances present on your skin. The best Kit. If you don’t have the kit, you can purchase these leads
choice is disposable latex or nitrile exam gloves, which at a local Radio Shack or other electronics supply store.
are inexpensive and sufficient to protect your hands from
Chapter 2 : Equipping Your Forensics Laboratory 15Light sources convenient and inexpensive source is the disposable
Several lab sessions require a bright light source, aluminum pie pans sold in supermarkets. Buy a pack.
such as a small desk lamp. (If you have a work surface These can also be used as drying dishes.
that is illuminated by bright natural light, the lamp is
unnecessary.) Examining opaque objects under the Plastic sheet, transparent
microscope requires a source of incident (top) illumination. Lab IV-5, Revealing Latent Fingerprints On Sticky Surfaces,
We use a white LED book light with a flexible neck, which optionally uses a plastic sheet as a fingerprint transfer
allows positioning the angle and distance of the light. You sheet. The transparent plastic sheets sold for overhead
can also use a bright desk lamp or other light source. transparencies or as notebook sheet protectors are
suitable.
Mesh, fiberglass
Lab Session I-2, Examine the Physical Characteristics of Pipettes, plastic graduated
Soil, involves sifting soil specimens through a mesh to Plastic graduated pipettes are used for measuring and
separate particles by size. The FK01 Forensic Science Kit transferring small amounts of liquids (see Figure 2-10). The
includes a suitable piece of mesh, but you can substitute pipettes supplied with the FK01 Forensic Science Kit are
any similar mesh, such as a piece of window screen or a graduated with four lines on the stem of the pipette at 0.25,
kitchen flour sifter. 0.5, 0.75, and 1 mL. They can also be used to measure
very small amounts of dilute aqueous solutions because
Microscope slide, cross-sectioning they deliver about 36 drops per mL, which translates to
A cross-sectioning slide is a standard plastic or metal about 27.8 microliters per drop. (This value may differ for
microscope slide drilled with a small hole or holes. Fibers solutions that are more or less viscous than water.) If you
are drawn through the hole and then cut flush with the don’t have the kit, these pipettes can be purchased from
top and bottom of the slide using a scalpel or razor blade any lab supply vendor.
to allow viewing the fibers in cross section through the
microscope. The FK01 Forensic Science Kit includes a
drilled plastic cross-sectioning slide. You can purchase Figure 2-10: Graduated plastic pipettes
metal versions of these slides from forensic supply vendors
or make your own by drilling a plastic slide or using a
heated needle to melt a hole in it.
Modeling clay
Modeling clay is included in the FK01 Forensic Science
Kit, but can also be purchased from toy, hobby, and craft
stores. It’s used to mount small opaque specimens for
viewing under the microscope.
Paint chips
Lab I-2, Examine the Physical Characteristics of Soil,
requires a selection of soil-colored paint chips, which you
can obtain at a hardware store or paint store.
Pie pans, disposable aluminum Plates, reaction and spot
Lab VI-1, Tool Mark Analysis, requires thin aluminum The FK01 Forensic Science Kit includes a 24-well
sheets, thicker than foil, for making tool marks. One polystyrene deep-well reaction plate with a lid, shown in
16 DIY Science: Illustrated Guide to Home Forensic Science ExperimentsFigure 2-11. This reaction plate is used in many lab sessions piece of mesh, which allows separating the specimens into
for running chemical tests, mixing or diluting solutions, and two fractions. Optionally, you can use other mesh sizes
so on. The FK01 kit also includes a 12-well polypropylene to separate the specimens into three or more fractions.
shallow-well spot plate. The 12-well plate is used for Household items such as a flour sifter or a fine mesh metal
liquids—strong acids, solvents, and so on—that may coffee filter can be used to do this.
damage the polystyrene plate. If you don’t have the kit, you
can purchase these plates from any lab supply vendor. Small items
The FK01 Forensic Science Kit includes a flat/spoon
Figure 2-11: A reaction plate microspatula, a ruler, and a stirring rod. If you don’t have
the kit, you can purchase these items from any lab supply
vendor, or substitute similar household items.
Steam iron (or oven)
Lab session IV-3, Revealing Latent Fingerprints Using
Ninhydrin, requires a steam iron (by preference) or a
kitchen oven.
Test tubes and accessories
The FK01 Forensic Science Kit includes six test tubes, a
test tube clamp, and a test tube rack. If you don’t have the
kit, you can purchase these items from any lab supplies
vendor.
Timer
Ruler Several lab sessions require timing with more or less
The FK01 Forensic Science Kit includes a standard accuracy. Any watch or clock with a second hand is
6"/150 mm ruler. If you don’t have the kit, you can sufficient for these sessions.
substitute any millimeter-graduated ruler.
Transfer sheets
Scalpel Lab session II-1, Gathering Hair Specimens, requires
The FK01 Forensic Science Kit includes a standard transfer sheets to contain the hair specimens you obtain.
disposable scalpel. If you don’t have the kit, you can You can use something as simple as index cards or even
purchase a scalpel from any lab supplies vendor or sheets of paper.
substitute a single-edge razor blade.
Table 2-2 summarizes the laboratory equipment we
Sieves recommend.
Lab I-2, Examine the Physical Characteristics of Soil,
involves separating soil specimens into fractions based on
particle size. The FK01 Forensic Science Kit includes one
Chapter 2 : Equipping Your Forensics Laboratory 17Table 2-2: Recommended laboratory equipment
Item FK01 Sources
○
Balance (optional) Lab supply vendors
Beaker, 100 mL (glass or polypropylene)● Lab supply vendors
Beaker, 250 mL (glass or polypropylene)● Lab supply vendors
●
Bottle, sprayer Drugstores
Burner, gas○ See text
Centrifuge tubes, 1.5 mL● Lab supply vendors
●
Centrifuge tubes, 15 mL Lab supply vendors
Centrifuge tubes, 50 mL● Lab supply vendors
Chromatography paper● Lab supply vendors
○
Digital voice recorder (optional) See text
Dishes, drying○ See text
●
Filters, plane-polarizing (2) Lab supply vendors
●
Fingerprint brush Forensic supply vendors
Forceps● Lab supply vendors
○
Fuming chambers See Text
Gloves○ Drugstores, supermarkets
Goggles, chemical splash● Lab supply vendors
●
Graduated cylinder, 10 mL (glass or polypropylene) Lab supply vendors
Graduated cylinder, 100 mL (glass or polypropylene)● Lab supply vendors
Inoculating loop● Lab supply vendors
○
Lab notebook (bound composition book or similar) Office supply vendors
Leads, alligator clip (2; red and black)● Electronics supply vendors
○
Light sources See text
●
Mesh, fiberglass Hardware stores
Modeling clay● Toy/hobby/craft stores
●
Needle, dissecting (teasing), bent Lab supply vendors
Needle, dissecting (teasing), straight● Lab supply vendors
Paint chips○ See text
18 DIY Science: Illustrated Guide to Home Forensic Science ExperimentsItem FK01 Sources
○
Pie pans, disposable aluminum Supermarkets
Pipettes, plastic, graduated● Lab supply vendors
Plastic sheet, transparent (optional)○ See text
●
Plate, reaction, 24-well polystyrene with lid Lab supply vendors
Plate, spot, 12-well polypropylene● Lab supply vendors
Ruler, millimeter scale● Office supply vendors
●
Scalpel Lab supply vendors
Sieves (optional)○ See text
Slide, microscope, cross-sectioning● Forensic supply vendors
●
Spatula Lab supply vendors
Steam iron (or oven)○ See text
●
Stirring rod Lab supply vendors
●
Test tube clamp Lab supply vendors
Test tube rack● Lab supply vendors
●
Test tubes Lab supply vendors
Timer (watch or clock with second hand)○ Obtain locally
Toothpicks, plastic○ Supermarkets
○
Transfer sheets See text
chemicals and Reagents
In addition to the equipment described in the previous section, you’ll need an assortment of
raw chemicals and reagents to complete the lab sessions. (Broadly speaking, raw chemicals are
materials that are supplied and used as-is in pure form or as simple solutions, while reagents are
specic m fi ixtures of chemicals, usually in liquid form.)
The word reagent has two meanings in lab parlance: a reagent may be a mixture of chemicals, and often bears a person’s
name. For example, Marquis reagent is a mixture of the raw chemicals sulfuric acid and formaldehyde. But “reagent” is also
used to specify a purity grade for raw chemicals. Chemicals that are specified as “reagent,” “reagent grade,” or “ACS reagent
grade” meet specific purity standards, are assayed to determine their exact contents, and are extremely pure. Reagent-grade
chemicals are suitable for the lab sessions in this book but are often purer (and more expensive) than actually necessary. For
most of the lab sessions in this book, laboratory-grade, USP-grade, or another relatively pure grade of chemicals is sufficient.
Chapter 2 : Equipping Your Forensics Laboratory 19All of the lab sessions that require special reagents include Ammonia, household (clear, non-sudsy)
instructions for preparation of those reagents from raw Two lab sessions require ammonia, which is not included
chemicals. If you make up these reagents yourself, be sure in the FK01 Forensic Science Kit. Household ammonia is
to follow all safety procedures, including reading the MSDSs generally a 5% to 10% concentration, which is fine for our
(Material Safety Data Sheets) for the chemicals you use. Always purposes. Get the clear, non-sudsy version.
wear goggles, gloves, and protective clothing while making up
and using these reagents. Ascorbic acid (vitamin C) tablets, 500 mg
The FK01 Forensic Science Kit includes 500 mg ascorbic
Acetone acid (vitamin C) tablets. If you don’t have the kit or if you
Several lab sessions require acetone, which is not included require additional tablets, simply use standard 500 mg
in the FK01 Forensic Science Kit. You can purchase pure vitamin C tablets.
acetone in pint (500 mL) or quart (1 L) containers at any
hardware store or paint store. Baking soda (sodium bicarbonate)
One lab session requires baking soda, which is not included
Agar powder in the FK01 Forensic Science Kit. Use ordinary baking soda
The FK01 Forensic Science Kit includes 10 grams of agar from the supermarket.
powder, which is used in the DNA gel electrophoresis
lab session. If you don’t have the kit, you can purchase Bleach, chlorine laundry
agar from a lab supply vendor. You can also substitute Two lab sessions require chlorine laundry bleach, which is
food-grade agar, which sells for a few dollars per ounce not included in the FK01 Forensic Science Kit. Use ordinary
in some supermarkets and most stores that sell Chinese 5.25% sodium hypochlorite bleach. The cheap, no-name
and Japanese specialty foods. The gelling quality of food- stuff is fine.
grade agar is variable, so we recommend using twice the
amounts specified in the lab session. Blood, synthetic
The FK01 Forensic Science Kit includes synthetic blood,
Alcohol, ethyl (ethanol), 95% which mimics the chemical behavior of actual blood. If you
Several lab sessions require ethanol, which is not included don’t have the kit, you can purchase synthetic blood from
in the FK01 Forensic Science Kit. You can purchase a forensic supply vendor, or simply substitute actual blood
95%/96% ethanol under that name or as ethyl alcohol in from raw meat or another source. (Note that there are
hardware and paint stores. Most drugstores carry 70% several types of synthetic blood available. Theater blood
ethanol, which is not ideal but is generally usable. is designed to look like real blood, but is unsuitable for our
purposes. Synthetic blood designed for use in spatter-
Alcohol, isopropyl (isopropanol), 99% pattern analysis is also unsuitable. If you buy synthetic
Several lab sessions require isopropanol, which is not blood, you want the type used for training analysts on
included in the FK01 Forensic Science Kit. You can blood detection activities.)
purchase 99% isopropanol under that name or as isopropyl
alcohol in some hardware stores. Most drugstores carry Buffers, DNA loading and running
70% isopropanol, which is not ideal but is generally usable. The FK01 Forensic Science Kit includes a 6X concentrate of
Some drugstores also carry 91% isopropanol, which is DNA loading buffer and a 20X concentrate of DNA running
superior to the 70% concentration for our purposes. buffer. If you don’t have the kit, you can make up these
buffers yourself or purchase them from forensic supply
vendors or general lab supply vendors.
In general, ethanol and isopropanol can be used
interchangeably for the lab sessions in this book.
Sometimes one or the other yields superior results. If we
specify one and you don’t have it, the other will almost
certainly work.
20 DIY Science: Illustrated Guide to Home Forensic Science Experiments
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