Molecular genetics - forensics

Specimen:
  1. Criminal investigation: specimens (blood, semen, hair, skin from under the fingernails) obtained from the victim are matched against specimens (usually 5mL blood in EDTA) from the suspect(s).

  2. Identity and paternity testing: 5mL blood in EDTA or 1-2 drops from a capillary sample for a child.

    Specimens are collected from the index case and from purported relatives.

    Other specimens eg, saliva, plucked hair roots may be accepted by legislation in the future.

    Consult pathologist prior to organising specimen collection.

See also Paternity testing.

Method:

See Molecular genetics.

Amplification by PCR with a range of DNA polymorphisms known as short tandem repeats (microsatellites) is now more commonly used than RFLPs.

Application:

Identification of individuals suspected of having committed serious crime eg, rape, murder.

Establishing the identity of an otherwise unidentifiable corpse, if likely close relatives are available for testing.

Determination of paternity by confirming or refuting a biological parental relationship.

Interpretation:

The results, in a forensic context, are usually expressed as a frequency of the analysed profile (specimens from the victim) in the general population and its degree of similarity or difference from the specimen collected from the suspect.

When establishing a biological relationship the results are usually expressed as a probability of paternity or exclusion of paternity.

See also RCPA Catalogue of Genetic Tests and Laboratories.

Reference:

Hochmeister MN. Molecular Aspects of Medicine 1995; 16: 315-417.