Note Taking: How Crime Scene Investigation Works
Note Taking: How Crime Scene Investigation Works
Note Taking: How Crime Scene Investigation Works
Documentation of the scene begins with the first responder. Police officers are taught the
importance of taking notes from the time of arrival. The crime scene investigator documents
the scene in the form of still and video photography. Sketches are completed at the scene to
illustrate relationships between articles of evidence not easily depicted by photography. The
following methods of crime scene documentation are used to provide an accurate
representation of the scene.
Note Taking
It is important that the responding officers note the condition of the scene as it existed upon
their arrival. Note taking should be continuously updated during the course of the
investigation.
The primary means of crime scene documentation is still photography. Police officers should
have an understanding of the importance of keeping the scene preserved, and not moving
anything until it is photographed. The photographer must be able to testify that the
photograph is a true and accurate representation of the scene at the time the photograph was
taken. Crime scene photographs should reveal a detailed, chronological story of the scene.
Sketching
Photographs may not always depict spatial relationships between objects; sketches are used to
supplement photographs. Sketches can more easily depict the overall layout of the scene and
the relationships between objects. Investigators usually complete hand-drawn, rough sketches
while at the crime scene. These sketches contain all the necessary information for the
investigator to subsequently complete a finalized version.
For courtroom presentation, hand drawn sketches may be converted using computerized
programs such as computer aided design (CAD), which provide a dynamic, professional
appearance.
Police officers are typically the first to arrive at a crime scene. They arrest the perpetrator is he's still there and
call for an ambulance if necessary. They are responsible for securing the scene so no evidence is destroyed.
The CSI unit documents the crime scene in detail and collects any physical evidence.
The district attorney is often present to help determine if the investigators require any search warrants to
proceed and obtain those warrants from a judge.
The medical examiner (if a homicide) may or may not be present to determine a preliminary cause of death.
Specialists (entomologists, forensic scientists, forensic psychologists) may be called in if the evidence requires
expert analysis.
Detectives interview witnesses and consult with the CSI unit. They investigate the crime by following leads
provided by witnesses and physical evidence.
At the Crime Scene: Finding the
Evidence
With theories of the crime in mind, CSIs begin the systematic search for incriminating
evidence, taking meticulous notes along the way. If there is a dead body at the scene, the
search probably starts there.
Before moving the body, the CSI makes note of details including:
After moving the body, he performs the same examination of the other side of
the victim. At this point, he may also take the body temperature and the ambient
room temperature to assist in determining an estimated time of death
(although most forensic scientists say that time of death determinations are
extremely unreliable -- the human body is unpredictable and there are too many
variables involved). He will also take fingerprints of the deceased either at the
scene or at the ME's office.
Once the CSI is done documenting the conditions of body and the immediately surrounding
area, technicians wrap the body in a white cloth and put paper bags over the hands and feet
for transportation to the morgue for an autopsy. These precautions are for the purpose of
preserving any trace evidence on the victim. A CSI will usually attend the autopsy and take
additional pictures or video footage and collect additional evidence, especially tissue samples
from major organs, for analysis at the crime lab.
• The inward spiral search: The CSI starts at the perimeter of the scene
and works toward the center. Spiral patterns are a good method to use
when there is only one CSI at the scene.
• The outward spiral search: The CSI starts at the center of scene (or at
the body) and works outward.
• The parallel search: All of the members of the CSI team form a line. They
walk in a straight line, at the same speed, from one end of crime scene to
the other.
• The grid search: A grid search is simply two parallel searches, offset by 90
degrees, performed one after the other.
• The zone search: In a zone search, the CSI in charge divides the crime
scene into sectors, and each team member takes one sector. Team
members may then switch sectors and search again to ensure complete
coverage.
While searching the scene, a CSI is looking for details including:
• Are the doors and windows locked or unlocked? Open or shut? Are there
signs of forced entry, such as tool marks or broken locks?
• Is the house in good order? If not, does it look like there was a struggle or
was the victim just messy?
• Is there mail lying around? Has it been opened?
• Is the kitchen in good order? Is there any partially eaten food? Is the table
set? If so, for how many people?
• Are there signs of a party, such as empty glasses or bottles or full
ashtrays?
• If there are full ashtrays, what brands of cigarettes are present? Are there
any lipstick or teeth marks on the butts?
• Is there anything that seems out of place? A glass with lipstick marks in a
man's apartment, or the toilet seat up in a woman's apartment? Is there a
couch blocking a doorway?
• Is there trash in the trash cans? Is there anything out of the ordinary in the
trash? Is the trash in the right chronological order according to dates on
mail and other papers? If not, someone might have been looking for
something in the victim's trash.
• Do the clocks show the right time?
• Are the bathroom towels wet? Are the bathroom towels missing? Are there
any signs of a cleanup?
• If the crime is a shooting, how many shots were fired? The CSI will try to
locate the gun, each bullet, each shell casing and each bullet hole.
• If the crime is a stabbing, is a knife obviously missing from victim's
kitchen? If so, the crime may not have been premeditated.
• Are there any shoe prints on tile, wood or linoleum floors or in the area
immediately outside the building?
• Are there any tire marks in the driveway or in the area around the
building?
• Is there any blood splatter on floors, walls or ceilings?
The actual collection of physical evidence is a slow process. Each time the CSI collects an
item, he must immediately preserve it, tag it and log it for the crime scene record. Different
types of evidence may be collected either at the scene or in lab depending on conditions and
resources. Mr. Clayton, for instance, never develops latent fingerprints at the scene. He
always sends fingerprints to the lab for development in a controlled environment. In the next
section, we'll talk about collection methods for specific types of evidence.
Evidence Collection
In collecting evidence from a crime scene, the CSI has several main goals in mind:
Reconstruct the crime, identify the person who did it, preserve the evidence for analysis and
collect it in a way that will make it stand up in court.
Trace evidence
Trace evidence might include gun-shot residue (GSR), paint residue, chemicals, glass and
illicit drugs. To collect trace evidence, a CSI might use tweezers, plastic containers with lids,
a filtered vacuum device and a knife. He will also have a biohazard kit on hand containing
disposable latex gloves, booties, face mask and gown and a biohazard waste bag.
If the crime involves a gun, the CSI will collect clothing from the victim and anyone who
may have been at the scene so the lab can test for GSR. GSR on the victim can indicate a
close shot, and GSR on anyone else can indicate a suspect. The CSI places all clothing in
sealed paper bags for transport to the lab. If he finds any illicit drugs or unknown powders at
the scene, he can collect them using a knife and then seal each sample in a separate, sterile
container. The lab can identify the substance, determine its purity and see what else is in the
sample in trace amounts. These tests might determine drug possession, drug tampering or
whether the composition could have killed or incapacitated a victim.
Technicians discover a lot of the trace evidence for a crime in the lab when they shake out
bedding, clothing, towels, couch cushions and other items found at the scene. At the CBI
Denver Crime Lab, technicians shake out the items in a sterile room, onto a large, white slab
covered with paper.
CBI Denver trace-evidence room
The technicians then send any trace evidence they find to the appropriate department. In the
Denver Crime Lab, things like soil, glass and paint stay in the trace-evidence lab, illicit drugs
and unknown substances go to the chemistry lab, and hair goes to the DNA lab.
Body fluids
Body fluids found at a crime scene might include blood, semen, saliva, and vomit. To
identify and collect these pieces of evidence, a CSI might use smear slides, a scalpel,
tweezers, scissors, sterile cloth squares, a UV light, protective eyewear and luminol. He'll
also use a blood collection kit to get samples from any suspects or from a living victim to use
for comparison.
If the victim is dead and there is blood on the body, the CSI collects a blood sample either by
submitting a piece of clothing or by using a sterile cloth square and a small amount of
distilled water to remove some blood from the body. Blood or saliva collected from the body
may belong to someone else, and the lab will perform DNA analysis so the sample can be
used later to compare to blood or saliva taken from a suspect. The CSI will also scrape the
victim's nails for skin -- if there was a struggle, the suspect's skin (and therefore DNA) may
be under the victim's nails. If there is dried blood on any furniture at the scene, the CSI will
try to send the entire piece of furniture to the lab. A couch is not an uncommon piece of
evidence to collect. If the blood is on something that can't reasonably go to the lab, like a wall
or a bathtub, the CSI can collect it by scraping it into a sterile container using a scalpel. The
CSI may also use luminol and a portable UV light to reveal blood that has been washed off a
surface.
If there is blood at the scene, there may also be blood spatter patterns. These patterns can
reveal the type of weapon that was used -- for instance, a "cast-off pattern" is left when
something like a baseball bat contacts a blood source and then swings back. The droplets are
large and often tear-drop shaped. This type of pattern can indicate multiple blows from a
blunt object, because the first blow typically does not contact any blood. A "high-energy
pattern," on the other hand, is made up of many tiny droplets and may indicate a gun shot.
Blood spatter analysis can indicate which direction the blood came from and how many
separate incidents created the pattern. Analyzing a blood pattern involves studying the size
and shape of the stain, the shape and size of the blood droplets and the concentration of the
droplets within the pattern. The CSI takes pictures of the pattern and may call in a blood-
spatter specialist to analyze it.
A CSI might recover carpet fibers from a suspect's shoes. The lab can compare these fibers to
carpet fibers from the victim's home. Analysts can use hair DNA to identify or eliminate
suspects by comparison. The presence of hair on a tool or weapon can identify it as the
weapon used in the crime. The crime lab can determine what type of animal the hair came
from (human? dog? cow?); and, if it's human, analysts can determine the person's race, what
part of the body the hair came from, whether it fell out or was pulled and whether it was
dyed.
Fingerprints
Tools for recovering fingerprints include brushes, powders, tape, chemicals, lift cards, a
magnifying glass and Super Glue. A crime lab can use fingerprints to identify the victim or
identify or rule out a suspect. There are several types of prints a CSI might find at a crime
scene:
• Visible: Left by the transfer of blood, paint or another fluid or powder onto
a surface that is smooth enough to hold the print; evident to the naked
eye
• Molded: Left in a soft medium like soap, putty or candle wax, forming an
impression
• Latent: Left by the transfer of sweat and natural oils from the fingers onto
a surface that is smooth enough to hold the print; not visible to the naked
eye
A perpetrator might leave prints on porous or nonporous surfaces. Paper, unfinished wood
and cardboard are porous surfaces that will hold a print, and glass, plastic and metal are non-
porous surfaces. A CSI will typically look for latent prints on surfaces the perpetrator is likely
to have touched. For instance, if there are signs of forced entry on the front door, the outside
door knob and door surface are logical places to look for prints. Breathing on a surface or
shining a very strong light on it might make a latent print temporarily visible. When you see a
TV detective turn a doorknob using a handkerchief, she's probably destroying a latent print.
The only way not to corrupt a latent print on a non-porous surface is to not touch it. Proper
methods for recovering latent prints include:
A casting kit might include multiple casting compounds (dental gypsum, Silicone rubber),
snow wax (for making a cast in snow), a bowl, a spatula and cardboard boxes to hold the
casts.
If a CSI finds a footwear impression in mud, she'll photograph it and then make a cast. To
prepare the casting material, she combines a casting material and water in a Ziploc-type bag
and kneads it for about two minutes, until the consistency is like pancake batter. She then
pours the mixture into the edge of the track so that it flows into the impression without
causing air bubbles. Once the material overflows the impression, she lets it set for at least 30
minutes and then carefully lifts the cast out of the mud. Without cleaning the cast or brushing
anything off it (this would destroy any trace evidence), she puts the cast into a cardboard box
or paper bag for transport to the lab.
For toolmark impressions, a cast is much harder to use for comparison than it is with
footwear. If it's not feasible to transport the entire item containing the tool mark, a CSI can
make a silicone-rubber cast and hope for the best. There are two types of tool marks a CSI
might find at a crime scene:
Firearms
If a CSI finds any firearms, bullets or casings at the scene, she puts gloves on, picks up the
gun by the barrel (not the grip) and bags everything separately for the lab. Forensic scientists
can recover serial numbers and match both bullets and casings not only to the weapon they
were fired from, but also to bullets and casings found at other crime scenes throughout the
state (most ballistics databases are statewide). When there are bullet holes in the victim or in
other objects at the scene, specialists can determine where and from what height the bullet
was fired from, as well as the position of the victim when it was fired, using a laser
trajectory kit. If there are bullets embedded in a wall or door frame, the CSI cuts out the
portion of the wall or frame containing the bullet -- digging the bullet out can damage it and
make it unsuitable for comparison.
Documents
A CSI collects and preserves any diaries, planners, phone books or suicide notes found at a
crime scene. He also delivers to the lab any signed contracts, receipts, a torn up letter in the
trash or any other written, typed or photocopied evidence that might be related to the crime.
A documents lab can often reconstruct a destroyed document, even one that has been burned,
as well as determine if a document has been altered. Technicians analyze documents for
forgery, determine handwriting matches to the victim and suspects, and identify what type of
machine was used to produce the document. They can rule out a printer or photocopier found
at the scene or determine compatibility or incompatibility with a machine found in a suspect's
possession.
Whenever a CSI discovers a piece of evidence at the scene, she photographs it, logs it, -
recovers it and tags it. An evidence tag may include identification information such as time,
date and exact location of recovery and who recovered the item, or it may simply reflect a
serial number that corresponds to an entry in the evidence log that contains this information.
The crime scene report documents the complete body of evidence recovered from the scene,
including the photo log, evidence recovery log and a written report describing the crime
scene investigation.