Genetics and Crime: Forensic Science Fundamentals

Introduction to Forensic Science and Genetics

• Focus of Lecture: Discuss the intersection of genetics and crime, emphasizing forensic developments over time.
• Warning for Comfort: Acknowledgment of sensitive topics (e.g., sexual assault, murders) and encouragement to leave if uncomfortable.

Historical Context and Initial Cases

• Traditional Forensic Methods: Early reliance on fingerprints and blood samples (e.g., type A blood).
• Narborough, England Case (11/21/1983): 15-year-old Linda Mann vanished and was found murdered and sexually assaulted.
  • Initial forensic analysis showed type A blood and unique enzyme panels narrowing suspects to 10% of the population.
• Subsequent Case: Another victim, 15-year-old Dawn Ashworth, also assaulted by the same perpetrator as Mann.
  • Similar blood type and enzyme panel led police to suspect the same individual.
  • Suspect Richard Buckland was adamant about his innocence regarding Mann's case but knew details about Ashworth's murder.

Development of DNA Forensics

• Alec Jeffries and DNA Analysis: Police chief referred samples to dr. Alec Jeffries, who identified that both victims were assaulted by the same person.
  • Jeffries' work introduced the first significant DNA investigation known as the "DNA manhunt."
  • Involvement of local males (5,000-7,000) for blood samples, though most results were negative.
• Colin Pitchfork: Eventually identified as the suspect after discussing his past crimes in a pub. Arrested after testing matched the DNA from the crime scenes.

Restriction Fragment Length Polymorphism (RFLP)

• Understanding RFLP: Technique employed by Jeffries for analyzing DNA.
  • **Process:
    1. Isolate DNA from samples.
    2. Treat with restriction enzymes to create fragments.
    3. Perform gel electrophoresis to separate based on size.
    4. Transfer to membrane for radioactive labeling.
  • RFLP is highly effective for differentiation between samples.
• Restriction Enzymes: Cut specific DNA sequences and create different fragments, useful in identifying genetic markers.

Case Studies of DNA Evidence

• **Notable Individuals:
  • Richard Buckland:** Exonerated as the first individual based on DNA evidence after being wrongfully accused.
• Tommy Andrews Case: First U.S. conviction based on DNA evidence (February 1988) after previously being acquitted.
  • Evidence linked to semen samples found at various crime scenes.

Comparison of Techniques

• **RFLP vs. VNTR:
  • RFLP:** Requires larger DNA amounts, more complex, expensive, and multiple steps for analysis.
  • VNTR: Uses PCR amplification, can work with smaller samples, quicker and cheaper throughput.
• Main Takeaways: DNA fingerprinting is mostly used to exclude individuals, emphasizing the importance of solid confirmations in forensic investigations.

Contemporary Case Reference

• OJ Simpson Case: Cross-examination of blood samples from a crime scene and suspect.
  • Highlighted potential errors in sample handling and collection processes.
  • Despite overwhelming evidence, Simpson was acquitted due to procedural issues, showcasing the significance of forensic validity in court.

Conclusion

• The lecture wraps up with an emphasis on the evolution of forensic science and genetics, showcasing how these advancements shape current and future investigations into crimes.