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Chapter 2
Protective Clothing Worn at the Crime Scene
Coveralls/ jumpsuits worn over clothing Removed afterwards and searched for
evidence before throwing away. Surgical gloves are worn the entire
time on the scene Masks and hair nets are worn most of
the time to protect from contamination Booties are worn over shoes to prevent
evidence from being contaminated
Primary Crime Scene- Where the crime actually occurred
Secondary Crime Scene- In some way related to the primary scene, but not where the crime occurred (i.e. body dump, getaway car, hideout)
Search Patterns- Spiral
Start on the inside and work your way in or vise versa.
Start at one edge and make a line up and down throughout the entire search area.
Search Patterns- Strip/Line
Search Pattern- Grid
Complete a strip/line search and begin a search in perpendicular rows to the already searched areas.
Search Patterns- Quadrant
Break up the area into small search areas and individuals search their own quadrant before moving on the next.
5 Steps to Processing a Crime Scene
Interview Examine Photograph Sketch Process
Step 1: Interview Begins once the Crime Scene
Investigator arrives at the scene The first responding officer makes
sure there is no longer a threat, he/she assists any victims, then preserves the crime scene.
The first responding officer is interviewed as well as any victims and witnesses
Step 1…Continued The FR should try to detain the person
who made the report. (He/she does not know if they are a witness or a suspect.) Others on the scene may also need to be detained
He/she must create a “security log” of who is going in and out.
This helps the CSI form a theory of what may have happened and potential evidence to look for
Step 2: Examine
Examine the scene to see if the theory he/she thinks is what the evidence shows
The CSI looks for potential evidence that would be beneficial to the case as well as a point of entry and exit to the scene
Step 3: Photograph
Photographs taken to give an overall view of the scene
2 Categories of photos: Overall views- zoomed out, full
room views Items of evidence- pictures of
evidence photographed with a scale
Step 3: Photograph
35mm cameras are still used for pictures
Tripods can be used when taking close ups or many pics in one area
Digital photos can be easily altered, so they are not used as much
Details of evidence and position
Camera setting Time, date,
location Photographer taking the picture
Documentation of Photograph
Step 4: Sketch Sketching the crime scene is a way to
pictorially show where things were found once you leave the scene.
Must create a “rough sketch” while at the scene. Measure all items , furniture, and room
dimensions Measurements should be made from
fixed points The rough sketch is kept with the
investigators notes
Step 4: Sketches
Final sketches are sometimes made for use in court. Must be drawn to scale with a legend All evidence including the body is
shown and measurements from fixed points are shown
Step 5: Process
Processing the scene means to search and obtain all of the evidence from the scene.
2 forms of evidence collected Testimonial evidence form witnesses Physical evidence which is tangible
Types of Evidence Physical Evidence- nonliving or
inorganic (fibers, paint, drugs, bullets, …etc.)
Biological Evidence- organic (blood, saliva, hair…etc.)
Reconstructive Evidence- any evidence that helps law enforcement gain a better understanding of what happened at a crime scene (broken glass, pried-opened doors/windows, trajectory of bullets) Determines who did what, where, when
and how
Types of Evidence
Associative Evidence- ties a suspect to the crime scene (could also disprove) Could be a fingerprint, hair,
shoeprint, blood…ect.
Collecting Evidence
Each type of evidence may have a specific way to be collected and packaged
Fibers and Hairs Use forceps to collect Collect items of clothing from suspects
and victims and bag Collect vacuum sweepings from each
room and package separately
Collecting Evidence
Fingernail scrapings Collect with a dull pick much like a
toothpick Put all of the scrapings into a bag labeled
with location, date, time, case number and person collecting the sample.
Collecting Evidence from a Victim
Autopsies are performed on deceased victims
Evidence such as the following must be collected: Clothing Fingernail scrapings Blood DNA
Collecting Evidence from a Victim
Once a body is buried getting evidence off of it takes time and has to go through the court system (exhumation)
As a medical examiner, you must get all of the evidence off of the body before burial or risk losing it
Evidence Collection
Each piece of evidence must be placed in a separate bag or container and labeled with Date, Time, Location
and Collector
Evidence Collection
Biological samples that are susceptible to bacterial or fungal contamination should not be kept in an air-tight container Blood Semen….etc
Chain of Custody
A list of all persons who come in contact or possession of an item of evidence
Used in court to account for the where-abouts of evidence since collection
Evidence must be properly labeled and a chain of custody record must be kept
Standard/Reference Samples
Physical evidence whose origin is known such as blood, hair, glass or soil from a suspect that can be compared to crime scene evidence
Examples: Soil samples from all types of soil around the
crime scene Blood samples from the victim and the
suspect Samples of all medications found at the scene Hair samples of all persons at the scene
Substrate Control
Uncontaminated surface material close to an area where physical evidence has been deposited Glass samples Hair Soil Blood
Example of Control Sample A sample of charred carpet is thought to
have accelerant residue on it. It is compared to the same kind of carpet known to be free of the suspected materials. A carpet sample taken from an undamaged section of fire may provide the known sample. If a suspicious chemical is present in the charred carpet but not in the known sample, the lab can be more certain that there is a foreign chemical involved and not a component of the carpet or adhesive.
Individual vs. Class Class Characteristics
Properties not unique to a particular object, but place it into a particular group. .38 caliber gun, type B blood
Individual Characteristics Properties of an object that narrows down
the evidence to one person or a very small group of individuals Fingerprint on a .38 caliber gun, DNA of the
type B person
http://www.fws.gov/lab/csi_evidence.php
Direct vs. Circumstantial Evidence
Direct- establishes a fact (eyewitness statement, confessions), not as reliable b/c an eyewitness can be wrong
Circumstantial- requires that a judge and/or jury make an indirect judgment/inference about what happened (evidence identified through forensic science), more reliable
Recognizing a Staged Crime Scene
Most common- making a murder look like a suicide or accident (suspect may move the body or cleanup certain areas) Example: A husband strikes his wife on
the head with a blunt object, killing her. He cleans up the bedroom, moves her to the bathroom and puts her in the tub. He calls the paramedics and claims she fell while bathing.
Searching without a Warrant
1. In an emergency situation- a second entry at a later time would require a warrant.
2. Impending loss of evidence- for example, if a fire were going to destroy evidence.
3. Lawful arrest- the suspect and their property may be searched.
4. Consented search- the person has given permission.
Obtaining a Search Warrant
Must be specific about the time, place and items and must have probable cause approved by a judge
Only a law enforcement officer may obtain a warrant
Steps to Obtain a Warrant Prepare an affidavit- must describe
location to be searched, items to be looked for and the reason why the officer thinks they are there
Prepare warrant- this results in the document the judge must sign giving permission for the search to take place
Get the warrant signed- the officer must present the warrant and affidavit to the judge. If the judge agrees that probable cause exists, he/she will sign making the warrant official
Linking Criminals & Crime Scenes
NCAVC- National Center for the Analysis of Violent Crimes (throughout the country) This led to the development of VICAP (Violent
Criminal Apprehension Program) and PROFILER, which maintain profiles of serial murderers.
Data from crime scenes are entered into these databases. Investigators can take current cases and create profiles and compare it to those in the current database with the hopes of linking crimes & catching a perpetrator.