1. Crime Scene Investigation
Forensic Science

2. Crime Scene Team Police Officers (First Responders)
Usually first at scene
Secure Scene
District Attorney (possibly)
Sometimes present to determine if a search warrant is needed for crime-scene investigators
Crime-Scene Investigators
Document crime scene in detail and collect evidence
Recorders, sketch artists, photographers, evidence collectors
Medical Examiners (Also known as coroners)
May be present to determine the cause of death if a homicide or “possible” homicide occurred.
Detectives
Look for leads
Interview witnesses
Converse with CSI’s about evidence
Forensic Specialists
Certain crime scenes may call for experts in certain areas to be on scene
Example - entomologists

3. 7 S’s of Crime Scene Investigation
Securing the Scene
Responsibility of first-responding police officer (first responder)
First Responder = First crime scene
others may assist as they arrive
Safety of all individuals is FIRST priority
Preservation of evidence is SECOND priority
Tape off the area
Restrict all unauthorized persons from entering
Transfer, loss, or contamination of evidence can occur if the area is left unsecured
Log kept of all those that visit crime scene
Forensic experts (besides CSI) may be called in under certain circumstances

4. 7 S’s of Crime Scene Investigation
Separating the Witnesses
Witnesses should not be allowed to talk to each other
Otherwise could lead to collusion
Witnesses working together to create a story
Accounts of witnesses will be compared later
Are accounts the same or different
Do accounts match up with FORENSIC EVIDENCE?
The following questions should be asked
When did the crime occur?
Who called in the crime?
Who is the victim?
Can the perpetrator be identified?
What did you see happen?
Where were you when you observed the crime/crime scene?

5. 7 S’s of Crime Scene Investigation
Scanning the Scene
Determination of Primary Crime Scene and Secondary Crime Scene
Primary Crime Scene = location where initial crime took place
Example- Robbery site of a bank or store
Secondary Crime Scene = location other than primary crime scene where evidence may be found
Example- Home of a suspect in robbery
Determine where photos should be taken
Overall and up close of evidence

6. 7 S’s of Crime Scene Investigation
Searching for Evidence-
crime scene should be walked and location evidence marked.
Grid
Linear
Quadrant or Zone
Spiral
Xxx Xx xx

7. 7 S’s of Crime Scene Investigation
Seeing (photographing) the Scene
Photos of overall crime scene from several angles
Initial
Close up photos of evidence (including bodies) with and without a measuring ruler
After crime scene has been searched and evidence marked
Triangulation of stationary objects should be included in photos as reference points
Distance and location of evidence from stationary reference points
Example: location and distance of murder weapon from oak tree.

8. 7 S’s of Crime Scene Investigation
Securing and Collecting Evidence
ALL evidence needs to be properly packaged, sealed, and labeled
Protocol for packaging certain types of evidence exists to preserve evidence
Example- Most biological evidence must be place in breathable container so it can dry out (prevents mold)
Evidence then can be placed in paper bindle and then sealed in a plastic container or paper bag

9. 7 S’s of Crime Scene Investigation
Securing & Collecting Evidence
Paper Bindle- a folded paper
used to hold trace evidence
Crease a clean paper and place evidence in the X position
Fold in the left and right sides, and then fold in the top and bottom
Put the bindle into a plastic or paper evidence bag affixing a seal over the opening
Write your name on the seal

10. Maintaining Chain of Custody
Chain of Custody- the documented and
Sign over to a lab technician Open bag on non-sealed edge
unbroken transfer of evidence
Evidence should never be unattended
Return items to the evidence bag Seal evidence bag in another bag Sign the evidence log
Document each time evidence opened
Bag the evidence Add identification Seal it Sign it across the sealed edge

11. Example of Evidence Inventory Label
Include: Case #, Inventory #, Description of evidence

12. Analysis of Evidence Performed by forensic lab technicians
Usually very specialized
Example- DNA specialist, blood specialist ect…
Lab results can:
Show reliability of witness accounts
Establish the identity of suspects or victims
Show suspects to be innocent or link them with a scene or victim

13. 7 S’s of Crime Scene Investigation
Sketching the Crime Scene
An accurate rough sketch of the crime scene is made, noting the position of the body (if any) and any other evidence
All objects (evidence) should be measured from two immovable landmarks (reference points)
Direction of “North” should be labeled on sketch
Includes other objects (doors, chairs, windows, furniture ect…)
A Final sketch should be made for possible presentation in court
Drawn to scale (example 1/4 inch = ? Feet)
Computer programs are available to create neater and nicer sketch for court proceedings

14. 7 S’s of Crime Scene Investigation
Example of Sketch Format
Case number, date, location, and sketcher’s name should be included on rough and final sketch

15. Types of Evidence

16. Types of Evidence
Direct Evidence: includes first hand observations such as eyewitness account or police dashboard video cameras.
Example: Eyewitness, Photos, Video Tape

17. Types of Evidence
Circumstantial Evidence: is indirect evidence that can be used to imply a fact but that does not directly prove it. No one, other than the suspect and victim, actually sees when circumstantial evidence is left at the crime scene. This evidence can be physical or biological in nature.
Example: finding a gun at the suspect’s house, bloody knife, fingerprints, etc.

18. Trace Evidence
Trace evidence is a type of circumstantial evidence in which one object comes in contact with another object.
Known as Locard’s Exchange Principal
Examples:
Animal or Human Hair
Fingerprints
Soil of Plant Material (Pollen)
Body Fluids (Mucus, semen, saliva, or blood)
Fiber or debris from clothing
Paint Chips, broken glass, chemicals

19. Types of Circumstantial Evidence
Physical: Evidence not from living organisms
Examples: impressions such as fingerprints, footprints, shoe prints, tire impressions, and tool marks, gun, knife, car(not paint), pan.
Biological: From living organisms
Examples: body fluids, hair, plant parts, and natural fibers.

20. Classifications of Evidence
Class Evidence: narrows an identity to a group of persons or things. Knowing the ABO blood type of a sample of blood type that may have been there, excludes others.
Individual Evidence: narrows an identity to a single person or thing. Individual evidence typically has such a unique combination of characteristics that it could only belong to one person or thing, such as a fingerprint.

21. Legal Considerations at the Crime Scene
All removal of evidence from a person or from the scene must conform to the 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.

22. Warrantless Searches Existence of emergency situations
Prevent the immediate loss or destruction of evidence
Search of a person or property following a lawful arrest
Search by consent

23. Mincey v. Arizona
After a homicide, police searched a scene for four days. Evidence collected was found to be inadmissible in court because the court did not feel that evidence would have been lost or destroyed in the time needed to obtain a legal search warrant.

24. Michigan v. Tyler
Fire destroyed a building and evidence was collected the first day at the scene. After the initial entry, later entries into the building produced evidence. All evidence from later entries to the property were deemed inadmissible in court.