Forensic science unit 2 Flashcards
What is Locard’s exchange principle?
States that when a person comes into contact with an object or another person, a cross transfer of physical evidence can occur.
Example: Evidence from underneath a victim’s fingernails can help identify an attacker.
What are four examples of trace evidence?
- Hair
- Fibers
- Glass fragments
- Paint
Trace evidence refers to materials transferred from one location to another.
Distinguish between direct and circumstantial evidence.
Direct evidence is testimony or recordings of an event, while circumstantial evidence suggests a fact but does not prove it directly.
Examples: Testimony about seeing a crime is direct; fingerprints found at a scene are circumstantial.
What are the three steps of a crime scene investigation?
- Securing the scene
- Documenting the scene
- Collecting evidence
These steps ensure the integrity of the investigation.
Why is securing the crime scene important?
It prevents contamination of evidence and ensures the safety of individuals at the scene.
The first responding officer is typically responsible for this task.
What methods are used to document a crime scene?
- Photography
- Sketching
- Note-taking
Documentation is crucial for maintaining a record of the crime scene.
What is the difference between class and individual evidence?
Class evidence narrows an identity to a group, while individual evidence narrows it to a single person or thing.
Examples: ABO blood type is class evidence; DNA is individual evidence.
What factors can affect eyewitness testimony?
- Anxiety / Stress
- Race (Cross Race Effect)
- Drugs
- Contamination
- Circumstances
- Time
- Face attractiveness
- Location & Time of Day
These factors can lead to inaccuracies in identification.
What is an identity parade?
A police lineup process where a witness identifies a suspect from a group of individuals.
This process must be conducted fairly to ensure its admissibility in court.
What are the Seven S’s of Crime Scene Investigation?
- Secure the scene
- Separate the witnesses
- Scan the scene
- See the scene
- Sketch the scene
- Search for evidence
- Secure the collected evidence
These steps help ensure a thorough investigation.
What is the importance of maintaining a chain of custody?
It ensures the integrity of evidence and its admissibility in court.
A chain of custody log tracks who handled the evidence and when.
What is crime scene reconstruction?
Involves forming a hypothesis about the sequence of events surrounding a crime.
This process helps to establish a narrative based on collected evidence.
What are some common reasons for staging a crime scene?
- To cover up a financial crime
- To disguise a murder as a suicide
- To fake a burglary for insurance purposes
Staged crime scenes can mislead investigators.
Fill in the blank: Eyewitness misidentification is the single greatest cause of _______.
[wrongful convictions]
This statistic highlights the reliability issues surrounding eyewitness accounts.
What is the role of a lead detective in evidence analysis?
To see how facts fit into the crime scenario.
The lead detective coordinates the investigation and oversees evidence interpretation.
What is the correct procedure for packaging evidence?
Evidence should be placed in a clean paper, folded, put in a plastic or paper evidence bag, sealed, and labeled.
Proper packaging is essential to prevent contamination.
