Study Notes on Biological Evidence and Serology

Biological Evidence Overview

• Primarily related to blood and bodily fluids.

• Focus on serology: the science of analyzing fluids found at crime scenes.

Introduction to Serology

• Definition: Serology is the study and testing of bodily fluids, mainly blood.

• Importance:

  • Helps in identifying blood presence and type at a crime scene.

  • Different patterns and sources of fluids can yield distinct clues about events.

  • Precedes DNA testing, providing faster, on-site results.

Practical Applications

• Practice with blood patterns and splatter in class.

• Discussion of blood types and their significance in criminal investigations.

• Types of biological evidence explored:

  • Blood

  • Saliva

  • Semen

  • Urine

  • Sweat

Significance of Location

• The location of blood samples matters for reconstructing events:

  • Helps establish the angle and dynamics of injuries.

  • Indicates the likelihood of blood being tied to a specific incident.

Types of Testing

• Presumptive Testing:

  • Conducted on-site and provides quick, initial results.

  • Examples of substances that can cause false positives:

  • Potato juice

  • Bleach

  • Beet juice

• Confirmation Testing:

  • DNA testing to provide definitive identification.

  • Samples sent for testing require reasonable suspicion; backlog may cause delays.

Key Concepts of Blood Testing

• Types of blood tests:

  • Blood Typing: Determines the presence of antigens/antibodies.

  • Rh Factor: Indicates positive or negative status (e.g., A+, O-).

  • Blood type is a class characteristic, meaning multiple individuals can share the same type.

Example Scenario

• A suspect's blood type A- compared to a crime scene blood type A-.

  • Not definitive proof of guilt but increases suspicion.

  • A different blood type (e.g., O+) would likely exclude the suspect.

Evidence Handling Considerations

• Collection Methods:

  • Use paper bags for bloody evidence; plastic can promote mold growth.

  • Avoid contamination by wearing gloves and changing them frequently.

  • Always document evidence thoroughly:

  • Evidence log must include location, time, source, and handling details.

Specific Mistakes to Avoid in Evidence Collection

• Storing blood evidence in sealed plastic can result in mold formation.

• The importance of proper handling to maintain the integrity of samples.

Conclusion

• Emphasis on the importance of serology in forensic investigations.

• The distinction between serology and DNA testing in criminal investigations has significant implications for processing and handling evidence.