1. Forensic Science:The Crime Scene (Unit II) Physical Evidence- all objects that can establish whether a crime has been committed or can link a crime to a criminal or to a victim
Processing the Crime Scene
Securing and Isolating the Crime Scene
1st priority should be to give medical attention to those in need.
Then extensive efforts must be made to exclude all unauthorized personnel from the scene with ropes, barricades, or guards. Every person who enters the scene is a potential destroyer of physical evidence.
After the scene is secured, the lead investigator will:

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determine the boundaries of the scene
establish the perpetrator’s path of entry and exit
document and photograph obvious items related to the crime
perform an initial walk-through to gain an overview of the situation and develop a strategy for the systematic examination and documentation of the entire crime scene.
(only a limited amount of time!)
Record The Scene- 3 Ways (permanent records)
Photography- objects must not be moved
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until they have been photographed from all nec. angles.
Crime scenes should be photographed as completely as possible and should include the area where the crime took place and all adjacent areas where important acts occurred before or after the crime. Important areas include points of entry or exit, wall areas, the body from all angles relative to the entire scene, close ups of injuries, and weapons. When the size of the object is of importance, measuring scale (ruler)

4. may be placed by the object as a point of reference.
Still photographs offer most important details
Should include entire scene and surrounding area. Long-shots and close-ups are necessary- narration from one investigator is important
Video taping and digital computers have become more popular.

5. Sketches-
Rough Sketch- contains accurate dimensions and location of all important objects with reference to 2 fixed points.
Finished Sketch- drawn to scale with concern for aesthetic appearance. (used in court) CAD is becoming the tool of choice. – cool tool for scaling items to size.

6. - measurements need to be made with a tape measure and drawn to scale.
Give every piece of physical evidence a # or letter and provide a key.

7. Notes- Detailed written description of the scene with the location of items of physical evidence recovered. Must include time or discovery, and by whom and how it was packed and marked.
Taped recorded notes or narrating a video are much faster but need to be transcribed to written form.
May be the only written record years after.
May be needed to refresh someone’s memory.
Notes need to be very detailed.
Conducting a Search for Evidence
When possible, one person should be responsible for supervising the collection of evidence.

8. Should be done thoroughly to accusations of negligence, or “cover-up”.
Usually done by police or detectives. Forensic Scientists are only called in when the case is high profile.
Cross-transfer of evidence is useful in linking suspects to the crime site.
Thorough search for latent fingerprints is important.
For burglary, tool marks at point of entry are important.
For vehicle searches, the nature of the case determines how detailed the search must be.
Hit and run- undercarriage is examined for blood, hair, fibers, etc.
Homicide- all parts of the car are examined.

9. Physical evidence can be large or microscopic so critical areas should be vacuumed and sweepings submitted to the lab for analysis.
For assault or murder, the following must be collected and sent to the lab:
Victim’s clothing
Fingernail scrapings- use a dull object to avoid cutting the body
Head and pubic hairs
Blood (for DNA typing purposes
Vaginal, anal, and oral swabs (in sex related crimes
recovered bullets from the body
hand swabs from shooting victims (for gunshot residue analysis)
Autopsies- tissues and organs will be retained for pathological and toxicological examination
Once buried, evidence may be lost!

10. Collecting and Packaging Physical Evidence
Physical evidence must be handled and processed in a way that prevents any change from taking place between the time it is removed from the crime scene and the time it is received by the crime lab.
Changes may arise through contamination, breakage, evaporation, accidental scratching or bending, loss through improper or careless packaging.
Each item needs to be packaged separately to avoid cross contamination or damage.
Blood, hair, fibers or other trace evidence should normally not be removed from the item that bears them, the entire object (garment, weapon, etc..) should be sent to the lab. If not possible, blood scrapings or swabbing should occur, or remove specimen with a forceps.

11. Different items need to be packed differently. For example:
bloodstained materials need to be air-dried and packed in paper bags to avoid growth of mold.
Charred debris needs to be sealed in an airtight container to prevent the evaporation of volatile petroleum residues.
Maintaining Chain of Custody
Continuity of possession, or chain of custody, must be established whenever evidence is presented in court. Every person

12. who handles or examines the evidence must be accounted for.
Chain must be kept to a minimum!
Failure to substantiate evidence
chain of custody leads to questions
about the authenticity and integrity
of the evidence.
- Normally collector’s
initials, and dates of collection are
on the collected item

13. Crime Scene Safety
Increasing cases of AIDS and hepatitis B transmitted through exchange of body fluids have led to safety guidelines to protect investigators at crime scenes containing potentially infectious materials. These include:
wearing latex gloves and shoe covers
particle mask/respirator, goggles, or face shield
being alert to sharp objects, knives, needles, razor blades, etc..
No way of knowing Health Hazards!!!!!

14. maintaining red hazard bags for the disposal of contaminated gloves, pencils, etc...
Removal of torn garments
no eating, drinking, smoking or application of makeup at the crime scene.
Fingerprint brushes are used and then decontaminated.
Special laundry services for infectious linen
Legal Considerations at the Crime Scene
Removal of any evidence from a person or a crime scene must be done in conformity with Fourth Amendment privileges:

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“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizure, 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.”
Much valuable evidence submitted in court is excluded from use against the accused because of an “unreasonable” search and seizure of evidence.

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Investigators must obtain a search warrant before investigating and removing physical evidence at a crime scene. Exceptions to justify a warrantless search include:
emergency circumstances
the need to prevent the immediate loss or destruction of evidence
search made by the consent of the parties involved
search of a person and/or property after lawful arrest.