Forensics Unit 2

Direct Evidence

Testimony by a witness about what that witness saw, heard, or did. Video recording of the crime.

Circumstantial Evidence

Indirect Evidence, Trace Evidence. Types: Biological, Physical, Class, Individual.

Biological Evidence

E.G. Fingerprints, shoe tracks, tire marks, fibers, things not biological.

Biological Evidence

Blood, body fluids, hair, etc. Things originating from living creatures.

Class Evidence

Narrows down to a group of people or things.

Individual Evidence

Narrows down an identity to a single person or thing.

Locard’s Principle of Exchange

When a person comes in contact with an object or another person, a cross-transfer of physical material can occur.

Who is at Crime Scene?

- Police
- Crime scene investigator
- Medical examiners
- Detectives
- Specialist

Seven S’s

1. Secure the scene- Done by 1st responding officer
2. Separate witnesses- prevent them from talking to each other
3. Scan the scene- determine the crime scenes and what to photograph
4. Seeing the scene- Photos of the area are taken
5. Sketch the scene- a rough sketch and neater copy are made
6. Search for evidence- Walk the scene in pattern and mark location of evidence, photograph, sketch.
7. Secure collected evidence- Properly packaged, sealed, labeled.

Search patterns

Grid, Linear, Quadrant/Zone, Spiral.

Packaging evidence.

Crease clean paper and put evidence in the center, fold the sides and tuck in top and bottom, Put it into plastic bag and label.

Forensic Lab

Where evidence is processed revealing facts about the crime.

Lead detective

Aims to see how facts fit the scenario

Crime scene reconstruction

Form a hypothesis of the sequence of events from beginning to end.

Staged

Check if crime scenes are staged if things aren’t lining up.

Crime Scene Locations

Some crime scenes have multiple locations, primary - main scene, secondary - related to the crime scene with evidence.

DNA

1. Identify victim’s DNA and DNA of anyone else who had access to the evidence.

2. Prosecuters have to prepare for what happens in court.

3. if any dna doesn’t link to suspect, defense will claim it points to real criminal

4. Dna must be identified on all of the evidence
   
   

DNA collection and packaging

DNA evidence needs protection from
contamination
environmental damage
degredation