The forensic use of bioinformation

1. The forensic use of bioinformation

2. Forensic bioinformation Includes… • Fingerprints • DNA

3. Fingerprinting • The fingerprint is the most commonly used method of identification • No two people have the same fingerprints (including identical twins) • Fingerprints develop before birth and remain unchanged throughout life • Identification relies on the matching of patterns and the detection of certain ridge characteristics (Galtondetails)

4. DNA sample • From a person – a biological sample taken from an individual, usually a swab from the inside of a person’s cheek • From the crime scene - samples of biological material found at a crime scene that may be taken by scene of crime officers include blood, skin cells, semen, hair etc

5. DNA profiling • DNA from a sample is extracted, analysed and catalogued. • Sections of DNA are analysed for the presence of particular ‘markers’ • A DNA profile is a sequence of 20 numbers determined by these ‘markers’ DNA Profile

6. A DNA profile • Contains genetic information to help identify a person • On average, the chance of another (unrelated) person sharing the same 20 number profile as you is around one in a billion

7. How is bioinformation used by police? Fingerprints and a DNA sample are taken Arrest . Fingerprints are sent to NAFIS (National Automated Fingerprint Identification System) for checking A DNA profile is constructed from the sample – the profile is stored on the National DNA Database (NDNAD) The sample is kept in a fridge

8. Police check fingerprints and DNA profiles against crime scene samples from unsolved crimes If the DNA profile or fingerprint of a person matches a crime scene sample, this may be used as evidence in court that the person was involved in the crime

9. However…. Finding a persons DNA or fingerprint at a crime scene does not necessarily prove that they were involved in the offence… • It could have been planted at the scene, carried there on an object, or been transferred there via someone else’s clothing or shoes • The person may have been at the crime scene legitimately (e.g. they live there) or could be a witness/victim

10. Using DNA evidence in court • DNA profiling is generally a very reliable way of identifying a person BUT… • If a crime scene sample contains only tiny amounts of DNA, this can sometimes make the DNA profiling less reliable • DNA evidence in court is presented as statistics which can be confusing for people in the courtroom, including members of the jury • DNA can be contaminated before, during, or after the police and laboratory staff collect it and use it – care must be taken to try and avoid contamination

11. Using fingerprint evidence in court • Fingerprints are hard to analyse and trained experts must check them • Partial fingerprints are even harder to analyse • When fingerprint evidence in used in court, juries must be aware that when a match is declared, it is never a matter of scientific certainty or conclusive fact; it is the opinion of the expert

12. The forensic use of bioinformation quiz For each of the following statements you must work out the missing word

13. Question 1 No two people, even identical twins, have been found to have the same ____________?

14. Question 2 A DNA profile is recorded on the National DNA Database as a sequence of ______? numbers

15. Question 3 Fingerprints are stored on a database called ___________?

16. Question 4 On average the chances of two people sharing the same complete DNA profile is around one in a ____________?

17. Question 5 A DNA ____________? is a biological substance such as blood, skin, hair or semen