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Blood Typing Techniques in Forensic Investigations

Explore the use of blood typing in forensic science, including tests to determine blood presence, type, and distinction between human and animal blood. Learn how antigens, antibodies, and clotting play crucial roles in blood analysis. Engage in a practical blood mystery lab to apply your knowledge.

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Blood Typing Techniques in Forensic Investigations

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Presentation Transcript

  1. Warm-Up • List one thing you learned from the reading on Thursday.

  2. Blood Typing

  3. Review of “Forensics of Blood” • What are the 2 main tests to determine if blood is present? • Luminol and Kastle-Meyer (phenolphthalein/peroxide) http://www.youtube.com/watch?v=sF0Z0jJGwX8 • Do both tests work on human and animal blood? • How do we determine if the blood is human or animal? • Precipitin Test – presence of human blood revealed through clotting

  4. Review of “Forensics of Blood” • What are the 2 main tests to determine Blood Type of a blood sample? • Test for the presence of Antigens or Antibodies http://da.humanbiologi.wikia.com/wiki/Blodet

  5. Testing for Antigens • Recall: Antigens exist on the surface of red blood cells. • Either A or B • Type A – has A antigens • Type B – has B antigens • Type AB – has both A and B antigens • Type O – has neither antigens http://da.humanbiologi.wikia.com/wiki/Blodet

  6. Blood Clotting http://www.edu.pe.ca/threeoaks/teacherpages/higginbotham/Biology%20521%20Webpage/resources.htm

  7. Testing for Antigens • Recall: Antibodies: attach only to foreign antigens • A antigens produce anti-B antibodies • B antigens produce anti-A antibodies

  8. Testing for Antigens • Forensic scientists can inject antibodies to determine blood type: • Anti-a antibodies only bind to A antigens (forming a clot) • If clotting occurs when anti-a antibodies injected in blood, then blood is Type A or Type AB

  9. Testing for Antibodies • Forensic Scientists inject A or B cells into a blood sample to identify antibody present • If clotting occurs when A-Cells are injected, then anti-A antibodies are present and the sample is either Type B or Type O

  10. Review ABO Blood Typing Lab • Which of the two blood typing methods did we use in the lab? Testing for antigen or antibody? • Support your answer. • Grades: as long as you typed your blood correctly based on your results, you received full credit for data collection.

  11. Blood Mystery Lab • You will be completing another lab today – this will a 100 pt lab • You should be able to complete the entire lab in class, if you use your time wisely. • You will follow the lab instructions, but will also be asked several questions throughout the lab

  12. Blood Mystery Lab: Report Requirements • Background Section • 3-5 sentences explaining blood typing. • Materials Section • List all materials used in the lab. • Results: • All data tables drawn on a separate sheet of paper. • Conclusion: • Separate page for all written answers. • Complete sentences for all answers.

  13. Groups • Nik, Saul, Alison • Luke, Cynthia, Samantha • Jason, Crystal, Gabby • Darrick, Cesar, Lindsey • Victoria, Hailey, Blake • Brandon, Madi R., Shawn • Alexis, Chris, Jesus • Noe, Katherine, Madi M. • Callan, Aubrey, Marcus • Kyle, Kelcey, Gara • Nancy, Kayla, Malik • Alex, Courtney, Carolina

  14. Background You will work as a group to answer questions about blood typing.

  15. Background Section • You will have 10 minutes to work with your partners to draft/write your background section. • Discuss the following questions: • Why do we use blood typing to solve crimes? • How do we test for blood type? • What are the limitations of blood typing? • You may discuss the answers to these questions as a group, but you must all write your own background section.

  16. Data Collection: Part 1 We will come back to materials. Save room in your lab report to list your materials.

  17. Police Report: Police are called to a house where they discover a body near the back door. There is a fresh pool of blood by the victim's head. Officers question the neighbors and learn that a plumber and an electrician made service calls to the house just hours before. They are able to trace both. They recover a shirt with dark stains from the service van of the plumber and rags with similar dark stains from the electrician's van

  18. Samples sent to Lab: • Your forensics lab receives the following items to test: • Sample 1: Stained cloth from the plumber's van • Sample 2: Stained cloth from the electrician's van • Sample 3: Blood collected from under the victim's head

  19. Your Task: • First, test the shirt and rags to determine if the stains are caused by blood. • Go to your workstation and place a drop of phenolphthalein/peroxide solution on each stain. • A purple-violet color reaction indicates that blood may be present. The absence of this reaction indicates that blood is not present. Record your results.

  20. Conclusion The following slide contains the questions for Part 1. I suggest you start a new page to answer these questions.

  21. Part 1 Questions: • Why do we use the Kastle-Meyer test instead of Luminol? • From your lab: • Based on the results of this test, which person, the plumber or the electrician, becomes your chief suspect? • Support your answer. • Can you rule out the other suspect? Why or why not?

  22. Data Collection: Part 2

  23. Part 2 • When confronted, your chief suspect claims to have had a nosebleed, thus accounting for the bloodstain. investigators have now been able to recover a blood sample (Sample 4) from the suspect's van. lt is suitable for blood typing. You ask for and receive a blood sample from the suspect (Sample 5).

  24. Part 2 Questions: • Why should we type both suspect 4 and 5? • Read the instructions in your lab for blood typing. • Which method of blood typing are we using (finding antigens or antibodies)? Support your answer.

  25. Part 2: Data Collection • Follow the instructions in your lab to find the blood type for each sample.

  26. Results: Part 2 Be sure to include a data table in your final report that includes all of the data collected during this part of the lab.

  27. Part 2: Recording Data

  28. Conclusion: Part 2 The following slide has the remaining questions for the lab. These should be added to the end of your questions from part 1.

  29. Post Lab Questions: • Based on your results, did the blood collected from the suspect's van come from the suspect? • Support your answer. • Could this blood have come from the victim? • Support your answer. • Based on evidence, who is your prime suspect? Did it change from Part 1? Why or Why not? • What would be your next step in this investigation? • Can you rule out either person as a suspect? Why or why not?

  30. Materials Draft a list of all materials used in this lab.

  31. Closure • At the end of your lab report answer the following questions (note - there is no write or wrong answer): • What was the most challenging aspect of the lab? • What did you like about completing the lab this way (with all of the steps & questions outlined in the PPT)? • What did you dislike about completing the lab this way?

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