Crime Scene and Physical Evidence
What are the correct steps taken when a crime scene is approached, searched, and an investi-
gation is begun?
tion, and securing of evidence. If those three components are not carefully maintained the
evidence cannot be used in a court of law – which is in fact the purpose of evidence!
▪ vestigation, and all the way through the investigation itself.eginning of a crime scene in-
▪ Students will be able to list the details of each the jobs assigned during a crime scene in-
vestigation, and apply those skills to a model..
▪ Students will be able to recognize the importance of the use of chain of custody and
All the jobs combine during the crime scene investigation to produce evidence
that can be used in a court of law – leader, photographer, notetaker, sketcher,
and evidence collector.
The chain of custody for evidence must start at the crime scene and continue
throughout the investigation.
Different circumstances must be considered when searching for evidence out-
warrantless search is necessitated.the need for a warrant or determining if a
▪ Definition of forensics, Types of Analyses available in a crime lab
Saferstein, 8 edition, pg. 34-52
▯ Model 1 : Introduction to How Crime Scene Investigation Works
Video Clip: http://investigation.discovery.com/tv-shows/cold-
▯ At the Crime Scene : Scene Recognition At the Crime Scene : Scene
When a CSI arrives at a crime scene, he Documentation
doesn't just jump in and start recovering The goal of crime-scene documentation is
evidence. The goal of the scene recognition to create a visual record that will allow the
stage is to gain an understanding of what forensics lab and the prosecuting attorney to
this particular investigation will entail and easily recreate an accurate view of the scene.
develop a systematic approach to finding The CSI uses digital and film cameras,
and collecting evidence. At this point, the different types of film, various lenses,
CSI is only using his eyes, ears, nose, some flashes, filters, a tripod, a sketchpad, graph
paper and a pen. paper, pens and pencils, measuring tape,
• define the extent of the crime rulers and a notepad at this stage of the
scene. Is the scene the house and investigation. He may also use a camcorder
the immediate vicinity outside? Does and a camera boom.
it also include any cars in the • Note-taking at a crime scene is not
driveway? Is there a blood trail down as straightforward as it may seem. A
the street? CSI's training includes the art of
• Securing the crime scene -- and scientific observation…in crime
any other areas that might later turn scene investigations, opinions don't
out to be part of the crime scene -- matter and assumptions are harmful.
is crucial. Securing the scene When describing a crime scene, a
involves creating a physical barrier CSI makes factual observations
using crime scene tape or other without drawing any conclusions.
obstacles like police officers, police • CSIs take pictures of everything
cars or sawhorses, and removing all before touching or moving a single
unnecessary personnel from the piece of evidence. There are three
scene. types of photographs a CSI takes to
• get the district attorney involved, document the crime scene:
because if anyone could possibly • Overview shots are the widest
have an expectation of privacy in possible views of the entire
any portion of the crime scene, the scene.
CSI needs search warrants. • Mid-range photos show key
• begin a walk-through of the crime pieces of evidence in context.
scene by following a pre- • Close-ups of individual pieces
determined path that is likely to of evidence, showing any serial
contain the least amount of numbers or other identifying
evidence that would be destroyed by characteristics.
walking through it. During this • Every photo must be written in a
initial walk-through, he takes photo log. This log documents
immediate note of details that will the details of every photo,
change with time: What's the includes the photograph number,
weather like? What time of day of a brief description, the location,
day is it? He describes any notable the time, the date, any other
smells (gas? decomposition?), descriptive details that might be
sounds (water dripping? smoke relevant.
alarm beeping?), and anything that • CSIs also create sketches to depict
seems to be out of place or missing. both the entire scene, and particular
• call in any specialists or additional aspects of the scene that will benefit
tools that might be needed based on from exact measurements. The goal
particular types of evidence seen is to show locations of evidence and
during the recognition stage. how each piece of evidence relates At the Crime Scene : Finding the At the Crime Scene : Evidence
The goal of the evidence-collection stage is In collecting evidence from a crime scene,
to find, collect and preserve all physical the CSI has several main goals in mind:
evidence that might serve to recreate the Reconstruct the crime, identify the person
crime and identify the perpetrator in a who did it, preserve the evidence for
manner that will stand up in court. Evidence analysis and collect it in a way that will make
can come in any form. Some typical kinds it stand up in court.
of evidence a CSI might find at a crime • Trace evidence
scene include: Trace evidence might include gun-shot
• Trace evidence (gunshot residue, residue (GSR), paint residue, chemicals,
glass and illicit drugs. To collect trace
paint residue, broken glass, evidence, a CSI might use tweezers, plastic
unknown chemicals, drugs) containers with lids, a filtered vacuum
• Impressions (fingerprints, footwear, device and a knife. He will also have a
• Body fluids (blood, semen, saliva, biohazard kit on hand containing
vomit) disposable latex gloves, booties, face mask
and gown and a biohazard waste bag.
• Hair and fibers • Body fluids
• Weapons and firearms evidence Body fluids found at a crime scene might
(knives, guns, bullet holes, cartridge include blood, semen, saliva, and vomit. To
casings) identify and collect these pieces of
• Questioned documents (diaries, evidence, a CSI might use smear slides, a
suicide note, phone books; also scalpel, tweezers, scissors, sterile cloth
squares, a UV light, protective eyewear and
includes electronic documents like luminol.
answering machines and caller ID • Blood spatter patterns. These patterns
units) can reveal the type of weapon that was
Examining the scene
used, which direction the blood came
There are several search patte