Forensic Evidence and Crime Scene Investigation

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Questions and Answers

What is Locard's exchange principle?

Locard's exchange principle states that when two objects come into contact with each other, a cross-transfer of materials occurs.

What are examples of trace evidence?

Hair
Skin cells
Clothing fibers
All of the above (correct)

Distinguish between direct and indirect (circumstantial) evidence.

Direct evidence proves an alleged fact, like eyewitness accounts, while circumstantial evidence implies facts without directly proving them.

What are some examples of direct evidence?

Both A and B (D) Signup and view all the answers

What are some examples of indirect evidence?

Footprints (B) Signup and view all the answers

Identify the type of professionals who are present at a crime scene.

First responders, district attorneys, crime scene investigators, medical examiners, detectives, and specialists. Signup and view all the answers

Summarize the 7 steps of a crime-scene investigation.

<ol> <li>Secure the scene 2. Separate witnesses 3. Scan the scene 4. Document with photos 5. Sketch the scene 6. Handle and package evidence 7. Provide forensic testimony.</li> </ol> Signup and view all the answers

Explain the importance of securing a crime scene.

Securing a crime scene protects evidence, preventing contamination and unauthorized access. Signup and view all the answers

What are the 4 crime scene search patterns?

Grid, linear, quadrant or zone, spiral. Signup and view all the answers

How to document a crime scene.

Photos of the area, close-up photos with and without a measuring ruler, sketches with measurements from landmarks, and labeling. Signup and view all the answers

Describe the various containers used to collect evidence and what kind of evidence each can hold.

Metal or plastic forceps for small items; plastic pill bottles for hair and fibers; airtight containers for liquids and arson evidence. Signup and view all the answers

What information is included in an evidence log?

Description of evidence, name of suspect and victim, date and time of recovery, signatures of recoverer and witnesses. Signup and view all the answers

Locard's exchange principle implies all of the following except:

Blood spatter can be used to identify blood type (C) Signup and view all the answers

Transfer evidence can include all of the following except:

Footprint (A) Signup and view all the answers

The reason it is important to separate the witnesses at the crime scene is to:

Prevent the witnesses from talking to each other (D) Signup and view all the answers

Correct collection of evidence involves which of the following:

All of the above (D) Signup and view all the answers

A crime scene sketch should include all of the following except:

The type of search pattern used to collect the evidence (A) Signup and view all the answers

Explain how blood type, considered class evidence, could still be useful in an investigation.

Knowing the blood type can indicate that a person with that blood type may have been at the scene and can exclude others. Signup and view all the answers

What type of information would the recorder need to obtain from the first responding officer?

A security log of anyone visiting the crime scene and the time they arrived. Signup and view all the answers

What type of information would the recorder need to obtain from the photographer?

Photos of the overall area and close-up photos with and without a measuring ruler. Signup and view all the answers

What type of information would the recorder need to obtain from the sketch artist?

An accurate rough sketch noting the position of the body and any evidence. Signup and view all the answers

What type of information would the recorder need to obtain from the evidence collection team?

Case number, item inventory number, evidence description, names of suspect and victim, date and time of recovery, signatures of witnesses. Signup and view all the answers

For each type of situation, describe the type(s) of evidence that could be obtained when transporting a body in a closed body bag.

Trace evidence and the victim's body, such as bloody hair. Signup and view all the answers

For each type of situation, describe the type(s) of evidence that could be obtained by taking nail clippings from the deceased.

Cell skin. Signup and view all the answers

For each type of situation, describe the type(s) of evidence that could be obtained by placing a plastic bag over the hands of the deceased.

Cells, skin, or dust and fibers that have fallen into the hand. Signup and view all the answers

For each type of situation, describe the type(s) of evidence that could be obtained by brushing the clothing of the victim with a clothes brush.

Hair or fiber from the cloth. Signup and view all the answers

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Study Notes

Locard's Exchange Principle

When two objects contact, materials are exchanged, leading to evidence transfer.

Trace Evidence

Physical or biological materials at crime scenes include:
- Hair, skin cells, clothing fibers, makeup, soil, pollen.
- Fingerprints, body fluids (blood, saliva), broken glass, paint chips.

Direct vs. Circumstantial Evidence

Direct Evidence: Proves an alleged fact directly (e.g., eyewitness testimony).
Circumstantial Evidence: Implies a fact without direct proof, can link a crime to a suspect.

Examples of Evidence

Direct Evidence Includes:
- Eyewitness accounts, police dashboard camera footage.
Indirect Evidence Includes:
- Footprints, shoeprints, tire impressions, body fluids, hair, and natural fibers.

Crime Scene Professionals

First Responder: Initial police officer securing the scene.
District Attorney: Determines the need for search warrants.
Crime Scene Investigator: Collects evidence, documents the scene, sketches, and photographs.
Medical Examiner: Establishes cause of death.
Detectives: Interview witnesses and collaborate with investigators.
Specialists: Include entomologists, forensic scientists, and psychologists.

Steps of Crime Scene Investigation

Secure the scene to prevent contamination.
Separate witnesses to avoid story alteration.
Scan and photograph the scene from multiple angles.
Create sketches and properly handle evidence.
Provide forensic testimony during trials.

Importance of Securing a Crime Scene

Protects evidence from contamination; the first officer establishes barriers and security.

Crime Scene Search Patterns

Four methods: grid, linear, quadrant (zone), spiral.

Documenting a Crime Scene

Take overall and close-up photographs with measuring tools.
Sketch should include measurements from landmarks, labeling North, objects in context, and evidence details.

Evidence Collection Containers

Use metal or plastic forceps for small evidence.
Preferred containers: Plastic pill bottles for fibers and hair; airtight containers for liquids.

Evidence Log Information

Requires evidence description, suspect/victim names, recovery date/time, signatures of those involved.

Recognizing Evidence Types

Transfer evidence can occur through direct contact or contamination in crime scenes.
Blood type aids investigations by linking suspects to crime but is not definitive.

Information for Recorders at Crime Scene

Details needed from the first responder, photographer, sketch artist, and evidence collectors for accurate documentation.

Collecting Evidence from Victims

Body transport should maintain integrity of trace evidence.
- Nail clippings can yield skin cells.
- Placing bags over hands preserves additional evidence.
- Brushing clothing collects loose fibers or hair.

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