Unit 2: The Crime Scene
Learning Goals
Know: Steps taken at the crime scene
Understand: Reasoning behind steps and procedures
Be Able to: Explain basic crime scene investigation and evidence collection
Crime Scene Vocabulary
Crime Scene: Any physical location in which a crime has occurred or is suspected of having
occurred.
Primary Crime Scene: The original location of a crime or accident
Secondary Crime Scene: An alternate location where additional evidence may be found.
Suspect: Person thought to be capable of committing a crime
Accomplice: Person associated with someone suspected of committing a crime.
Alibi: Statement of where a suspect was at the time of a crime.
Introduction
The crime scene investigation team is responsible for recognizing, documenting, and
collecting evidence.
The evidence collected at a crime scene is all investigators have to go on to recreate a
picture of what happened at the scene.
Principle of Exchange
Physical transfer of materials such as hair, fibers, blood, and skin cells will occur whenever two
people come in contact with each other. Dr. Edmond Locard was the first to describe this
principle of exchange.
The longer or more intense the contact between two people, the greater amount of trace
evidence present.
It is the job of the forensic examiner to recognize, collect and analyze this trace evidence to
help solve crimes.
The Crime Scene Investigation Team
The team is made up of legal professionals, such as police officers and detectives, and scientific
professionals, such as a coroner and specialists like toxicologists, who work together to solve a
crime.
The 'Ideal' Crime Scene Team - Crime Scene Personnel
Police Officers
Police officers are usually the first to arrive at a crime scene.
The first responding police officer must make sure the scene is secure by first making
sure all individuals in the area are safe and second by preserving evidence.
Responsibilities - They are responsible for securing the scene and detaining persons of
interest.
Witnesses must not be allowed to talk to one another.
Team Leader
Gives directions and coordinates all work at the scene.
Photographer
Takes pictures of scene and evidence
Measurer
Takes measurements of the scene
Sketch Preparer
Makes the rough and final sketches of the scene.
Evidence Collector(s)
Collects, tags, and preserves evidence.
Master Note Taker
Logs observations, descriptions, and actions from the scene.
Additional Crime Scene Personnel
District Attorney
Often present to help determine if any search warrants are required to proceed and
obtains those warrants from a judge.
Medical Examiner (if a homicide)
May or may not be present to determine a preliminary cause of death.
Conducts the autopsy.
Specialists (Entomologists, forensic scientists, forensic psychologists)
May be called in if the evidence requires expert analysis
Detectives
Interview witnesses and consults with the CSI unit. They investigate the crime by following
leads provided by witnesses and physical evidence.
Working the Crime Scene (Actions)
Take care of emergency situations first
Render First-aid to victims if needed.
Deal with unsecured weapons
Identify, detain, and question person who reported the crime
May have vital information. May become a suspect
If possible, determine the perpetrator by inquiry or observation.
Detain everyone who is present at the scene - eyewitnesses to events prior to, during, and
after the crime
Statements should be taken when information is fresh.
Summon assistance if necessary - Crowd control, additional investigators
Physically secure the area. Use uniformed officers to:
Rope of the scene, limit access, secure witnesses
Working the Crime Scene - Precautions
Avoid touching or moving objects at the scene
Original state can never be restored.
Secure and investigate 'additional crime scenes'. Was a body or evidence moved?
Processing the Crime Scene
Step 1: Preserve Life
Get medical help for those who need it.
Arrest suspect
Step 2: Protect Area
Keep out all unauthorized people: Rope off, barricade, station guards
Assessing the Scene What evidence is here?
Physical Evidence
Any object that can establish that a crime has been committed or can provide a link
between a crime and its victim or between a crime and its perpetrator.
Analysis of a Crime Scene: 4 steps
Interview, Examine, Document, Process
Evidence must be recognized at the scene and preserved.
Crime Scene Records - Written
The first responder to the crime scene will note initial observations:
Condition of the scene - doors open/closed, furniture disturbed, etc.
Environment - Day/night, warm/cold, weather, odd smells, etc.
Actions - personal actions as well as those taken by witnesses.
Step 3: Photograph
The most important thing is for the scene to be in an unaltered condition
Objects must not be moved until photographed from all necessary angles.
Photographs should include:
Body position and location, close-ups of evidence, injuries, weapons
Place a ruler by objects for reference
Video evidence must follow the same rules.
Photos are taken in three ranges:
Overview shots - in an overlapping pattern
Allows investigators to piece together the whole scene
Mid-range shots - shows more detail and shows relative placement of nearby objects
Close-ups - of wounds or evidence and area under collected evidence. Shows most
detail.
Step 4: Sketching the Scene
A rough sketch and a neater final copy of the crime scene drawn to scale must be
made. Artistic skill is not necessary but it is an advantage
Rough Sketch - a draft representation of all essential information and measurements at
a crime scene. Must be drawn at the scene! Distances must be
measured from 2 fixed points (walls)
Finished Sketch - a precise rendering of the crime scene drawn to scale.
Drafting tools and computer programs are used.
3D scanners are very expensive but provide a complete and accurate representation of
the entire scene including placement of small evidence, blood spatter, bullet holes, etc.
Step 5: Notes
Detailed written description of crime scene and evidence. Provides the time and person who
found the evidence. Records who and how the evidence was packaged and where it was
sent.
The log includes: initial observations
Entry/exit of investigators and/or witnesses
Visual evidence records: photos, video, sketch, scan
Documentation of evidence: prior to collection and chain of custody after collection.
Record of search documents: copy of consent form and/or warrants
Step 6: Search
Systematic and thorough. Establish points of entry and exit.
Victim's body is also searched at autopsy.
Search at autopsy includes: examination of tissues and organs, victim's clothing,
fingernail scrapings, head and pubic hairs, blood,
vaginal, anal, and oral swabs, recovered bullets, hand
swabs from shooting victims.
The lead investigator will designate a search pattern appropriate to the crime and the scene.
Inward/Outward Spiral - a single investigator starts on the inside/outside of the scene
and slowly spirals out/in. Good for open areas or for scenes
with limited number of investigators.
Parallel/Grid - a line of investigators searches in one direction. In a grid they then go in
the other direction. Good when the area is clearly defined and a lot of
people are on hand.
Quadrant - a single investigator searches each quadrant. They may then switch
quadrants and repeat. Good for areas that can be clearly cut into fours square room, car, etc.
Step 7: Securing and Collecting the Evidence
All evidence must be properly packaged, sealed and labeled using specific techniques
and procedures. Avoid contamination. Keep evidence in original condition
Bloodstains are to be scraped off the surface or, transferred to a moist swab, or cut out
of the material depending on the situation.
The integrity of the sample must be maintained. Each different item or similar items
collected at different locations must be placed in separate containers to prevent damage
and cross contamination.
Standards/Reference Samples
Physical evidence whose origin is known such as blood or hair from a suspect that
can be compared to evidence found at a scene.
Can come from the crime scene, victim, suspect or any other known source.
Ex. paint from suspect car in hit and run used to compare to point on victim's
body
Buccal Swab
Swab of the inner portion of the cheek used to create a DNA profile. Must be taken of
victim and any suspects when blood or DNA is evidence.
Substrate Control
Uncontaminated surface material close to an area where physical evidence has
been deposited. Used to ensure that the surface where the sample was found
does not interfere with lab test.
Crime Scene Safety
1. Latex gloves (doubled) and shoe covers
2. Mask, goggles, face shield, coveralls
3. Biohazard bags and labels
4. Contaminated equipment must be disinfected with bleach solution
5. no smoking, drinking, or eating
Collection Tools: Forceps/tweezers, evidence tape, gloves, vacuum, swabs
Step 8: Packaging Evidence
Each piece of evidence should be wrapped in an appropriate sized bundle, placed
and sealed in an evidence bag, with the collector's signature along the taped edge.
An evidence log and a chain of custody must be attached to the evidence container.
Storing Evidence - small envelopes, plastic pill bottles, small cardboard boxes, glass vials
Packaging Wet Bloodstained Materials
- air dry in non-airtight containers. Avoids mold
Packaging Fire/Arson Evidence
- use airtight containers because they trap fumes.
Step 9: Chain of Custody
Each person who comes in contact with a piece of evidence must use proper
procedure and protocol in order to maintain responsible handling of evidence from
crime scene to courtroom.
Keep the chain as short as possible. Failure to maintain a chain of custody could
lead to evidence not being admissible in court.
Legal Considerations
Fourth Amendment
The right of the people to be secure in their persons, houses, papers, and effects, against
unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but
upon probable cause, supported by oath or affirmation, and particularly describing the
place to be searched, and the persons or things to be seized.
When is a Warrant NOT needed?
1. Emergencies
2. Prevent destruction of evidence
3. Immediate arrest
4. Permission already given/updated
Court Cases: Mincey v. Arizona and Michigan v. Tyler
Mincey v. Arizona
An undercover officer entered Mincey's apartment and was killed.
Police spend four days searching the apartment gathering bullets, drugs and other drug
paraphernalia. Mincey was convicted but won on appeal.
Michigan v. Tyler
Tyler co-owned a business that was destroyed by a late night fire.
The scene was unattended until 8 am. Officers searched the scene on three other
occasions (4, 7, and 25 days later) to convict Tyler and his partner of conspiracy to burn
down the business. The Supreme court upheld the reversal of conviction.