crime scene investigation & evidence collection

CRIME SCENE INVESTIGATION & EVIDENCE COLLECTION

CSI team and Crime lab

The Seven S’s of Cime Scene Investigation

Responsibilities of first officer1. Obtain medical assistance for anyone in need2. Arrest any perpetrators3. Exclude all unauthorized personnel4. Isolate the area5. Determine the boundaries of crime scene6. Entry and exit points of perpetrator7. Initial walk through8. Develop strategy for examining and documenting crime scene9. Determining primary and possible secondary crime scenes10. Document and photograph obvious evidence

Crime Scene Search Patterns

photographs

• Objects must NOT be removed until photographed from all angles

• If anything removed it should be noted and NOT be reintroduced

• Include photos of adjacent areas, close-ups of victim’s relative position in the scene and injuries

• If size is significant, a point of reference should be included in the photo

• Videotaping and narrating the crime scene can also be done

Scaled sketch of the crime scene

http://vimeo.com/45223797

The Frye Standard

Frye v. United States (1923) (polygraph test questioned)

The Frye Standard

Practical application:

Evidence

Direct Evidence

EvidenceCircumstantial (Indirect) Evidence

Locard’s Exchange Principle• Established by Dr. Edmond

Locard

Physical evidence

Biological evidence

• Control Sample:

• Standard/reference sample:

• Substrate control:

Packaging evidence

1. Create a clean paper and place evidence in the X position

2. Fold in the left and right sides, and then fold in the top and bottom

3. Put the bindle into a plastic or paper evidence bag affixing a seal over the opening

4. Write your name on the seal

Chain of Custody

– Provides documentation of every person who has come into contact with the evidence

– A paper trail– Demonstrates to the courts that the evidence that

is being presented at trial is free of contamination, alteration, or substitution

Bagging the evidence

1. Bag the evidenceAdd identification Seal itSign it across the sealed edge

2. Sign over to a lab technician Open bag on non-sealed edge

3. Return items to the evidence bagSeal evidence bag in another bagSign the evidence log

• Never package wet evidence while wet

• Blood stained material should NOT be stored in airtight containers due to mold potential. Paper bags or wrapping paper used.

• Air dry clothes and place in individual separate bags

• Charred debris from fire is sealed in airtight containers

• Facts result from collected evidence processed by the forensic lab

• Lead detective aims to see how facts fit into the crime scenario

• Lab results can show the reliability of witness accounts, establish identity of victim or suspects, show suspects innocence or link them with the crime.

Crime scene reconstruction

Crime scene reconstruction involves:

Staging

When lab results don’t match up with the testimony of witnesses

Common examples: