The identity of a dead person can be ascertained by;
- Identity papers –
- Dental records
- Genetic Fingerprint
Fingerprints: The skin on fingers, toes etc is ridged into specific patterns (arches, tented arches, whorls & loops). Sweat and sebum oil is left behind from our fingers on the things we touch. Using aluminium powder or protein stain (e.g. ninhydrin) fingerprints are revealed. Fingerprints are unique and can be used to identify people.
Dental Records: Can be used to identify age and to identify a person based on their dentist’s record of their teeth. This is usually used when the body is damaged (e.g. a corpse from a fire)
Figure 6.7 – On the record CR is a crown and BR is a bridge.
Genetic Fingerprint: Used because DNA is unique to individuals (except identical twins and clones grown by mad scientists). Genetic fingerprinting looks for the presence of repeated sequences of bases in the non-coding sections of DNA (introns). The repeated sequences are called satellites and can be 2 – 4 bases long (Micro-satellite) or 5 – 20 bases long (Mini- satellite). The satellites are repeated anything from 5 – 500 times and this produces a unique DNA signature.
- A sample of DNA is copied using PCR
- Sample is cut using a restriction enzyme
- Sample is run on an electrophoresis gel, often using a DNA sample of known length to act as a
- A southern blot is taken
- DNA is labeled using a DNA probe specific to the satellite
- An X-ray is taken to reveal the location of the bands of DNA
The fingerprint is the pattern of bands on the electrophoresis gel. Assuming the original DNA sample has not been contaminated (by e.g. a hair from the pathologist) the fingerprint will be exact. See Fig. 6.10.