Brazoria County Sheriff's Office
Identification Division
Crime Scene Investigation |
Once the crime scene has been thoroughly documented and the
locations of the evidence noted, then the collection process can begin. The collection
process will usually start with the collection of the most fragile or most easily lost
evidence. Special consideration can also be given to any evidence or objects which need to
be moved. Collection can then continue along the crime scene trail or in some other
logical manner. Photographs should also continue to be taken if the investigator is
revealing layers of evidence which were not previously documented because they were hidden
from sight.
Most items of evidence will be collected in paper containers such as packets, envelopes,
and bags. Liquid items can be transported in non-breakable, leakproof containers. Arson
evidence is usually collected in air-tight, clean metal cans. Only large quantities of dry
powder should be collected and stored in plastic bags. Moist or wet evidence (blood,
plants, etc.) from a crime scene can be collected in plastic containers at the scene and
transported back to an evidence receiving area if the storage time in plastic is two hours
or less and this is done to prevent contamination of other evidence. Once in a secure
location, wet evidence, whether packaged in plastic or paper, must be removed and allowed
to completely air dry. That evidence can then be repackaged in a new, dry paper container.
UNDER NO CIRCUMSTANCES SHOULD EVIDENCE CONTAINING MOISTURE BE PACKAGED IN PLASTIC OR PAPER
CONTAINERS FOR MORE THAN TWO HOURS. Moisture allows the growth of microorganisms which can
destroy or alter evidence.
Any items which may cross contaminate each other must be packaged separately. The
containers should be closed and secured to prevent the mixture of evidence during
transportation. Each container should have: the collecting person's initials; the date and
time it was collected; a complete description of the evidence and where it was found; and
the investigating agency's name and their file number.
Each type of evidence has a specific value in an investigation. The value of evidence
should be kept in mind by the investigator when doing a crime scene investigation. For
example, when investigating a crime he or she should spend more time on collecting good
fingerprints than trying to find fibers left by a suspect's clothing. The reason is that
fingerprints can positively identify a person as having been at the scene of a crime,
whereas fibers could have come from anyone wearing clothes made out of the same material.
Of course if obvious or numerous fibers are found at the point of entry, on a victim's
body, etc., then they should be collected in case no fingerprints of value are found. It
is also wise to collect more evidence at a crime scene than not to collect enough
evidence. An investigator usually only has one shot at a crime scene, so the most should
be made of it.
The following is a breakdown of the types of evidence encountered and how the evidence
should be handled:
Fingerprints (also includes palm prints and bare footprints)
are the best evidence to place an individual at the scene of a crime. Collecting
fingerprints at a crime scene requires very few materials, making it ideal from a cost
standpoint. All non-movable items at a crime scene should be processed at the scene using
gray powder, black powder, or black magnetic powder. Polaroid 665 black and white film
loaded in a Polaroid CU-5 camera with detachable flash should be used to make one-to-one
photographs of prints which do not readily lift. All small transportable items should be
packaged in paper bags or envelopes and sent to the crime lab for processing. Because of
the "package it up and send it to the lab" mentality, some investigators skim
over collecting prints at a crime scene. Collecting prints at the crime scene should be
every investigator's top priority. Fingerprints from the suspect as well as elimination
fingerprints from the victim will also be needed for comparison (the same holds true for
palm and bare footprints).
For more information on fingerprints see Fingerprints 1.01.
Bite marks are found many times in sexual assaults and can
be matched back to the individual who did the biting. They should be photographed using an
ABFO No. 2 Scale with normal lighting conditions, side lighting, UV light, and alternate
light sources. Color slide and print film as well as black and white film should be used.
The more photographs under a variety of conditions, the better. Older bitemarks which are
no longer visible on the skin may sometimes be visualized and photographed using UV light
and alternate light sources. If the bitemark has left an impression then maybe a cast can
be made of it. Casts and photographs of the suspect's teeth and maybe the victim's teeth
will be needed for comparison. For more information consult a forensic odontologist.
Much like a bullet that has individualizing striations on
it, natural fingernails have individualizing striations on them. A broken fingernail found
at a crime scene can be matched to the individual it came from many months after the crime
has been committed. Broken fingernails should be placed in a paper packet which is then
placed in a paper envelope. It can then be transported to the crime lab for analysis.
Known samples from the suspect and maybe from the victim will be needed for comparison.
Handwriting samples can also be matched back to the
individual that produced them. Known exemplars of the suspected person's handwriting must
be submitted for comparison to the unknown samples. Questioned documents can also be
processed for fingerprints. All items should be collected in paper containers. For more
information consult a questioned documents examiner.
If using the RFLP method of DNA analysis, then blood and
seminal fluid can be matched back to an individual with a high degree of probability.
Currently, if using the PCR method of DNA analysis or conventional serological techniques
then blood and some body fluids can be said to come from a certain population group to
which the individual belongs. As PCR technology advances, these population groups will
become smaller, eventually giving it the same discriminating power as RFLP analysis has
today. Dried blood and body fluid stains should be collected in the following manner: If
the stained object can be transported back to the crime lab, then package it in a paper
bag or envelope and send it to the lab; if the object cannot be transported, then either
use fingerprint tape and lift it like a fingerprint and place the tape on a lift back;
scrape the stain into a paper packet and package it in a paper envelope; or absorb the
stain onto 1/2" long threads moistened with distilled water. The threads must be air
dried before permanently packaging. For transportation purposes and to prevent cross
contamination, the threads may be placed into a plastic container for no more than two
hours. Once in a secure location, the threads must be removed from the plastic and allowed
to air dry. They may then be repackaged into a paper packet and placed in a paper
envelope. Wet blood and body fluid stains should be collected in the following manner: all
items should be packaged separately to prevent cross contamination, if the item can be
transported to the crime lab, then package it in a paper bag (or plastic bag if the
transportation time is under two hours), bring it to a secure place and allow it to
thoroughly air dry, then repackage it in a paper bag. If the item cannot be transported
back to the lab, then absorb the stain onto a small (1"x1") square of
pre-cleaned 100% cotton sheeting. Package it in paper (or plastic if the transportation
time is less than two hours), bring it to a secure place and allow it to thoroughly air
dry; then repackage it in a paper envelope. UNDER NO CIRCUMSTANCES SHOULD WET OR MOIST
ITEMS REMAIN IN PLASTIC OR PAPER CONTAINERS FOR MORE THAN TWO HOURS. Victim and suspect's
known whole blood samples will have to be collected in yellow, red, or purple top
"Vacutainers." Contact the lab to which the samples will be submitted for
specific information.
Bullets and casings found at the crime scene can be
positively matched back to a gun in the possession of a suspect. Bullets and casings can
also be examined at the crime lab and sometimes tell an investigator what make and model
of weapons may have expended the casing or bullet. A bullet found at the crime scene can
sometimes be matched back to the same lot of ammunition found in a suspect's possession.
Toolmarks can be positively matched to a tool in the suspect's possession. Firearm safety
is a must at any crime scene. If a firearm must be moved at a crime scene, never move it
by placing a pencil in the barrel or inside the trigger guard. Not only is this unsafe,
but it could damage potential evidence. The gun can be picked up by the textured surface
on the grips without fear of placing unnecessary fingerprints on the weapon. Before
picking up the gun, make sure that the gun barrel is not pointed at anyone. Keep notes on
the condition of the weapon as found and stops taken to render it as safe as possible
without damaging potential evidence. The firearm can then be processed for prints and
finally rendered completely safe. FIREARMS MUST BE RENDERED SAFE BEFORE SUBMISSION TO THE
CRIME LAB. The firearm should be packaged in an envelope or paper bag separately from the
ammunition and/or magazine. The ammunition and/or magazine should be placed in a paper
envelope or bag. It is important that the ammunition found in the gun be submitted to the
crime lab. Any boxes of similar ammunition found in a suspect's possession should also be
placed in a paper container and sent to the crime lab. Casings and/or bullets found at the
crime scene should be packaged separately and placed in paper envelopes or small cardboard
pillboxes. If knives (or other sharp objects) are being submitted to the lab (for
toolmarks, fingerprints, serology, etc.), then the blade and point should be wrapped in
stiff unmovable cardboard and placed in a paper bag or envelope. The container should be
labeled to warn that the contents are sharp and precautions should be taken. This is to
prevent anyone from being injured.
Shoeprints and tire tracks can be matched positively to a
pair of shoes or to tires in a suspect's possession. Shoeprints and tire tracks can
sometimes tell investigators what type of shoes or tires to look for when searching a
suspect's residence or vehicles. Before any attempt is made at collecting shoeprints or
tire tracks, one-to-one photographs should be made using a tripod, ruler, and level. The
flash should be held at about 45 degree angles from the surface containing an impression.
Casts can be made of impressions using dental stone. Once hardened, the cast can be
packaged in paper and submitted to the lab. When photographing prints on hard flat
surfaces the flash should be used as side lighting. Shoeprints on hard flat surfaces can
also sometimes be lifted like a fingerprint. Dust prints on certain surfaces can be lifted
with an electrostatic dustprint lifter.
Fracture matches can positively link broken pieces at the
scene with pieces found in the possession of a suspect. For example, headlight fragments
found at the scene of a hit and run could be positively matched to a broken headlight
(just like putting together a jigsaw puzzle) on a suspect's vehicle. Larger fragments
should be placed in paper bags or envelopes. Smaller fragments should be placed in a paper
packet and then placed in an envelope.
If a root sheath is attached, then DNA analysis using PCR
technology can say that this hair came from a certain percentage of the population to
which the suspect belongs. If there is no root sheath, then a microscopic analysis can say
that the hair has the same characteristics as the suspect's hair and is similar to his or
her hair. At this point, no one can say that a hair came from a particular individual.
Hair found at the scene should be placed in a paper packet and then placed in an envelope.
If a microscopic examination is required, then 15-20 representative hairs from the suspect
must be submitted to the lab for comparison. If DNA analysis if going to be used, then a
whole blood sample from the suspect must be submitted to the lab in a
"Vacutainer." Contact a DNA lab for more information.
Fibers can be said that they are the same type and color as
those found in a suspect's clothes, residence, vehicle, etc. Fibers should be collected in
a paper packet and placed in an envelope. Representative fibers should be collected from a
suspect and submitted to the lab for comparison.
Paint can be said that it is the same type and color as
paint found in the possession of a suspect. Paint fragments should be collected in a paper
packet and placed in an envelope. Representative paint chips or samples should be
collected from the suspect and submitted to the lab for comparison.
Glass can be said that it has the same characteristics as
glass found in the possession of a suspect. Smaller glass fragments should be placed in a
paper packet and then in an envelope. Larger pieces should be wrapped securely in paper or
cardboard and then placed in a padded cardboard box to prevent further breakage.
Representative samples from the suspect should be submitted to the lab for comparison.
Sometimes during the commission of a crime, there are other items which may be transferred to a perpetrator from the scene or from the perpetrator to the scene (sheetrock, safe insulation. etc.). The guidelines for collecting the evidence and obtaining known samples is about the same as for paint and fibers. For specific information, contact your crime lab.