The forensic use of bioinformation

Forensic bioinformation Includes… Fingerprints DNA

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 (Galton details)

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

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

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

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

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

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

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

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

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

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

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

Question 3 Fingerprints are stored on a database called ___________?

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

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