Forensics quiz 2 stuff..

Chapter 3: Physical Evidence

1. Physical Evidence - Any object that can establish that a crime has been committed or link a crime and its victim or perpetrator.

2. Identification - The process of determining a substance’s physical or chemical identity.

3. Comparison - The process of ascertaining whether two or more objects have a common origin.

4. Individual Characteristics - Properties of evidence that can be attributed to a common source with a high degree of certainty (e.g., fingerprints, DNA).

5. Class Characteristics - Properties of evidence that can be associated only with a group and not a single source (e.g., paint chips, fibers).

6. Forensic Databases - Computerized archives of information relating to physical evidence (e.g., CODIS for DNA, AFIS for fingerprints).

Chapter 4: Crime-Scene Reconstruction and Bloodstain Pattern Analysis

1. Crime-Scene Reconstruction - The process of determining or eliminating events that occurred at a crime scene by analyzing physical evidence.

2. Bloodstain Pattern Analysis - The study of bloodstains at a crime scene to establish the actions that led to their deposition.

3. Angle of Impact - The angle at which a blood droplet strikes a surface.

4. Area of Convergence - The point on a two-dimensional plane from which the bloodstains originated.

5. Area of Origin - The three-dimensional location from which the blood spatter emanated.

6. Spatter Pattern - Bloodstains created when blood is subjected to force and projected onto a surface.

7. Backspatter - Blood directed back toward the source of force.

8. Cast-Off Pattern - A bloodstain pattern created when blood is flung from a moving, blood-bearing object.

9. Transfer Stain - A bloodstain pattern created when a wet, bloody surface contacts another surface.

Investigation

• Physical Evidence - Any material object that plays a role in a criminal or civil matter and is used to prove a fact based on its physical characteristics.

• Patent Fingerprints - Visible impressions that can be seen without physical or chemical development.

  • Plastic Fingerprints - 3D impressions found in substances like clay, wax, soap, or mud.

  • Positive Fingerprints - 2D prints made by the transfer of a visible substance (e.g., blood, ink, oil, dirt) from a finger to a surface.

  • Negative Fingerprints - 2D prints made by removing material from a surface.

• Latent Fingerprints - Invisible 2D prints formed by the transfer of natural oils and sweat from a finger to a surface, requiring development to be made visible.

• Porous Surfaces - Materials such as paper, cardboard, fabric, and unfinished wood that absorb fingerprint residues.

  • Development methods: Iodine Fuming → Ninhydrin → Physical Developer

• Nonporous Surfaces - Smooth materials like glass, plastic, metal, and varnished wood that do not absorb fingerprint residues.

  • Development methods: Cyanoacrylate (super glue) fuming → Dye Staining → Fingerprint Powder

• Semi-porous Surfaces - Materials that are somewhat absorbent, such as magazines, glossy paper, book covers, and wallpaper.

  • Development methods must be researched case-by-case.

• Chain of Custody - The documented and unbroken transfer of evidence to ensure its integrity and admissibility in court.

• Crime Scene Investigation Steps:

  • Observe - Carefully examine the scene for potential evidence.

  • Evaluate - Judge the value and relevance of potential evidence.

  • Interpret - Explain the significance of an item or set of items.

  • Report - Document findings, how evidence was processed, and what the results could mean.

• Evidence Meaning and Analysis:

  • Fingerprint results can help determine suicide, homicide, accidental death, or natural death based on their presence or absence on key objects.

  • If a suspect’s fingerprint is found on a potential murder weapon, it suggests involvement in the crime.

  • The absence of a suspect’s fingerprint on a weapon could indicate they were not involved, or that they wore gloves.