F2: Crime Scenes & Evidence

2: Crime Scenes & Evidence Collection

Forensics
20245-25

Learning Targets, part 1

• Summarize Locard's Principle of Exchange

• Identify four examples of trace evidence

• Distinguish between direct and circumstantial evidence

• Identify the types of professionals who might be present at a crime scene

• Summarize the seven steps (7 S's) of a crime scene investigation.

• Explain the importance of securing the crime scene.

Learning Targets, part 2

• Identify the methods by which a crime scene is documented.

• Demonstrate proper technique in collecting and packaging trace evidence.

• Explain what it means to map a crime scene.

• Describe how evidence from a crime scene is analyzed.

​Vocabulary

• chain of custody

• circumstantial evidence

• class evidence

• crime scene investigation

• crime scene reconstruction

• datum point

• direct evidence

• first responder

• individual evidence

• paper bindleprimary crime scene

• secondary crime scene

• trace evidence

• triangulation

​Crime Scene Investigation

The process of recognizing, documenting, photographing, and collecting evidence from a crime scene.

Needed to solve the crime by providing evidence.

Trace Evidence

Small but measurable physical or biological material found at a crime scene.
.
Examples: hair, fibers, fingerprints, blood droplets, soil, pain chips, animal hair.

Locard's Principle of Exchange: When a person comes into contact with another person or an object, cross-transfer of trace evidence can occur.

Types of Evidence

1. Direct- if authentic, supports a fact in a case

   1. e.g. eyewitness accounts, video footage, confessions
      .

2. Indirect aka Circumstantial- implies a fact but does not directly support it

   1. can be physical or biological

   2. e.g. suspect's belongings found at a crime scene, foot prints, tool marks, DNA
      
      

Types of Evidence

1. Class evidence- narrows an identity to a group of people

   1. e.g. blood type, shoe size, etc.
      .

2. Individual evidence- narrows an identity to a single person or thing

   1. e.g. DNA evidence, fingerprint, machine marks, etc.
      
      

Crime Scene Investigation Team

• police officers arrive first and secure the scene

• crime scene investigators document the scene and collect evidence

• medical examiners / coroners determine the manner of death by examining a body

• detectives interview witnesses and talk to other team members about the evidence

• specialists may also be consulted

  • e.g. entomologists, forensic psychologists, etc.