Booklet to help with P7 M7 D7: Analysing biological evidence

1. Booklet to help with P7 M7 D7:Analysing biological evidence P7: Carry out practical work to analyse biological evidence. M7: Present valid conclusions drawn from the analysis of biological evidence. D7: justify the choice of techniques used to analyse the biological evidence.

2. Background knowledge on blood groups

3. Blood can contain antigens which can stimulate the immune system • There are two main types of antigens: Type A and Type B • A person’s blood group depends on what type of antigens their blood has

4. Blood groups based on antigens A and B The different blood groups are the following Type A Type B Type O Type AB

5. Blood groups based on Rh antigen • Individuals that have the Rh antigen are termed has being blood type “positive” • Individuals that do not have the Rh antigen are termed has being blood type “negative” • Examples: If a person has A and Rh antigens in their blood then their blood is Type A positive If a person has type A antigens but no Rh antigens in their blood then their blood is Type A negative

6. Task: What blood types do the individuals have based on what antigens their blood has?

7. What is blood typing? • Blood typing is using serums containing antibodies to determine what antigens a person’s blood contains. This can then be used to deduce what blood type the person is.

8. Why is blood typing important in forensics? • Blood is the most common bodily fluid found at crime scenes and is usually associated with violent crimes • After presumptive tests are used to determine that a fluid found at a crime scene is actually blood then we can use blood typing to start matching it up to suspects. • Then we can move onto analysing the blood from the crime scene and the suspects using DNA techniques

9. Why is blood typing important in forensics? • Blood typing is cheaper, quicker and easier to carry out than DNA analytical techniques • It is carried out first before DNA analytical techniques

10. P7: Carry out practical work to analyse biological evidence. Read the next three slides, then download the P7 assignment from unit 32 moodle page and carry out blood typing practical

11. How to determine a person’s blood type • Take a few drops of blood and place it into a blood typing tile • Then add the following anti-bodies: • Anti-A to well A • Anti-B to well B • Anti-Rh to well Rh

12. How to determine a person’s blood type • If there’s a reaction in any of the wells then you will see clumping. • The clumps are called “agglutinogens” • Use the table on the next slide to help you determine blood type

13. How to determine blood types

14. M7: Present valid conclusions drawn from the analysis of biological evidence Read the next slide, then download the M7 assignment from unit 32 moodle page and type up a conclusion

15. In your conclusion address the following questions: • Do any of the suspect’s blood samples match up to the blood found at the crime scene? • For each suspect how do you know what blood type they are? For example: “ When patient’s A blood was analysed there was clumping when the antibody Anti A was added to their blood so they have blood type A negative.” You will need to discuss each of the four patients one by one for this part of the conclusion

16. M7: Present valid conclusions drawn from the analysis of biological evidence Read the next slide, then download the D7 assignment from unit 32 moodle page and type up a paragraph justifying the techniques that we used

17. The techniques that we carried out • PARAGRAPH 1: explain what blood typing is, how it works and why it is important. • PARAGRAPH 2: State what apparatus was used AND explain WHY we used the apparatus The apparatus that we used was: • Blood typing spotted tile • Plastic rods • Anti-bodies: Anti-A, Anti-B, Anti-Rh