DNA profiling and matching of physical data, such as fingerprints, are used in solving all crime types ranging from housebreaking and car crime to assaults, murder and rape. The forensic scientists will look for suitable samples at a crime scene, examining such items as weapons, clothing, hair or anything else from which they can obtain body cells for DNA profiling, or fingerprints or "marks" for use in fingerprint matching.
The Scottish DNA database can help to solve undetected cases where there is no suspect. DNA profiling can also be used to identify a body formally. This is achieved by obtaining DNA profiles from both the mother and father or by relating personal effects to a body. DNA profiling is used in such cases after all other means of identifying a body have been carried out.
The details of a person's fingerprints are distinctive to them and only them. Even identical twins do not have identical fingerprints. A fingerprint can be left on many types of surfaces - a glass, a door, or a murder weapon for example. It can be made visible by brushing it with a powder or treating it with chemicals in a lab. Similarly, if the fingers are coated with ink or another substance such as paint, oil or blood, than a permanent impression may be left on a particular item.
Unknown fingerprints, or "marks" from a crime scene are compared by a fingerprint expert against known prints. The fingerprint expert will weigh up all of the information available and determine whether there is unique agreement between an unknown print and a known one which would confirm identity beyond all reasonable doubt.
The most crucial aspect of the fingerprint identification process is the verification element. This is an independent and complete analysis, comparison and evaluation of both prints which is carried out by a minimum of two fingerprint experts. The verification process is the key to the reliability of fingerprint evidence. Consistent results from different experts ensure the reliability of fingerprint evidence.