3 FingerprintingThe fingerprint is the most commonly used method of identificationNo two people have the same fingerprints (including identical twins)Fingerprints develop before birth and remain unchanged throughout lifeIdentification relies on the matching of patterns and the detection of certain ridge characteristics (Galton details)
4 DNA sampleFrom a person – a biological sample taken from an individual, usually a swab from the inside of a person’s cheekFrom 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 takenArrest.Fingerprints are sent to NAFIS (National Automated Fingerprint Identification System) for checkingA 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 shoesThe 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 generallya very reliable way ofidentifying a personBUT…If a crime scene sample contains only tiny amounts of DNA, this can sometimes make the DNA profiling less reliableDNA evidence in court is presented as statistics which can be confusing for people in the courtroom, including members of the juryDNA 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 themPartial fingerprints are evenharder to analyseWhen 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 quizFor each of the following statements you must work out the missing word
13 Question 1No two people, even identical twins, have been found to have the same ____________?
14 Question 2A DNA profile is recorded on the National DNA Database as a sequence of ______? numbers
15 Question 3Fingerprints are stored on a database called ___________?
16 Question 4On average the chances of two people sharing the same complete DNA profile is around one in a ____________?
17 Question 5A DNA ____________? is a biological substance such as blood, skin, hair or semen
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