Investigation and Evidence Collection - Chapter 2 HOSA Forensic Science

Investigation and Evidence Collection - Chapter 2 HOSA Forensic Science tfss 2023-24

Chain Of Custody

The documented and unbroken transfer of evidence from the crime scene to the laboratory, ensuring its integrity and admissibility in court.

Paper Bindle

A folded paper used to carefully package and preserve trace evidence, such as hair, fibers, or small particles, for further analysis.

Primary Crime Scene

The location where the crime actually took place, where the initial evidence is found, and where the most relevant information can be gathered.

Secondary Crime Scene

A location related to the crime where additional evidence is found, but it is not the primary location where the crime occurred.

Trace Evidence

Small, measurable amounts of physical evidence found at the crime scene

Locard’s Exchange Principle

Discovered by Dr. Edmond Locard

“When 2 people make contact, a physical exchange of many different materials can occurs called trace evidence”

Examples of trace evidence

hair, fibres, fingerprints

What decides the extent of the transfer?

3 factors:

• the intensity (how much contact?)

• Duration (how long?)

• Nature (what kind of contact?)

List the six types of evidences

Class Evidence

Individual Evidence

Direct Evidence

Circumstantial Evidence

Physical Evidence

Biological Evidence

Class Evidence

narrows suspect to a certain group of people (ex. blood group)

Individual Evidence

narrows suspect to a single person

Direct Evidence

Only Primary Observations; before or during the crime (ex. security camera footage, eye witness, audio recordings)

Circumstantial Evidence

Secondary observations, made by police or detectives on/after crime scene, (ex. footprints, hair)

Can you complete a case based on circumstantial evidence alone?

No, they can only provide a fact (there was a size 9 footprint on scene), not evidence of crime (size 9 committed crime.

Physical Evidence

Tangible objects, and impressions

Biological Evidence

Contains DNA. (ex. body fluids, hair)

Which is better, physical evidence or biological evidence?

Biological, since it is Individual Evidence and more convincing in court (rather than physical evidence, which is class evidence.)

Primary Crime Scene

Location where crime took place

Secondary Crime Scene

Not primary; Related to crime where evidence is found

Macroscopic Crime Scene

Crime scene that is visible or apparent to the naked eye (can be observed without the aid of magnification or detailed analysis.)

Microscopic Crime Scene

Involves evidence that requires specialized tools or techniques to observe or analyze

Three types of physical locations of crime scenes

Indoors, Outdoors, and vehicles

What is the objective of investigating a crime scene?

To recognize, preserve, collect, and interpret all physical evidence at a scene

What 5 people are on the investigation team?

1. Police Officers

2. Crime Scene Investigators

3. Medical Examiners

4. Detectives

5. Specialists

What does a FRO do? (5)

The FRO (or police officer)

• secures the scene

• verifies no one tampers with evidence

• get the search warrant approved

• call for “backup”

• separating witnesses

When do crime scene investigators arrive and what do they do?

They are usually second and document the scene by recording data, sketching scene and taking photos (for reconstruction)

What do Medical Examiners do?

Examine body for cause of death; only called in if body is present

Detectives (3)

They:

• look for leads

• interview witnesses

• talk to crime scene investigators

Specialists

Experts - contacted if needed

What does the Chain of Custody do? (2)

• ensures evidence is never lost

• accounts for everyone in contact

7 S’s in order

1. Securing the Scene

2. Separating Witnesses

3. Scanning Scene

4. Seeing the Scene

5. Sketching Scene

6. Searching for Evidence

7. Securing and Collecting Evidence

Securing the Scene (2)

• secured area to prevent evidence tampering/loss

• Call reinforcements and experts

Separating Witnesses (3)

• Do this to avoid communication between witnesses

• They are investigated (why, when, where, how, who?)

• When choosing witnesses, consider health, emotional state, mental wellbeing

Scanning Scene (2)

• identify evidence location, items to document

• identify primary + secondary crime scenes

Seeing the Scene (3.5)

• Crime Examiner Reviews scene

• Photos of the area are taken at different distances +angles

  • overall, midrange, closeup

• Body + Evidence are photographed for examination

what are the three different kinds of photo ranges?

• overall, mid-range, closeup

Sketching Scene (2.5)

• Rough sketch is done by crime examiners

  • includes positions of evidence + body

• Final sketch can be used as court evidence; accurate scale + compass

Searching for Evidence (2, methods + why)

• There are 5 different methods

  • Grid, Linear, Quadrant, Spiral, Wheel

• These ensure no evidence is missed

What 5 different searching methods are there?

• Grid

• Linear

• Quadrant

• Spiral

• Wheel

Securing and Collecting Evidence (3+1)

• evidence is placed into respective containers

• this is then placed in a paper bindle

• the container encasing the paper bindle needs to be

  • sealed with signed tape

  • upkeep evidence log + custody documents

How does crime reconstruction work (simplified)

putting evidence + witness statements together