For forensics, current DNA identification technologies measure short tandem repeat sequences (STRs) in the nuclear or mitochondrial DNA. The chosen STR sequences (typically 13 or more) are not linked to any known genetic characteristic, but vary from person to person in accordance with well-known population statistics. For this reason, measuring the lengths of these STRs provides a highly accurate and easily stored attribute that can be compared to others for potential identification, lead generation, exclusion, or family matching of an individual or individuals.
Determining the lengths of the STRs in a DNA sample involves some fairly advanced chemistry and associated processes. Before the advent of rapid DNA identification technology, this work was confined to certified laboratories with trained technicians and six different specialized laboratory instruments. Results usually came back after several days. Recent rapid DNA identification technologies have reduced this process down to one portable desktop instrument with automated processing taking about 90 minutes.
A feature of DNA identification, unique among the biometrics, is the ability to infer familial relationships via DNA testing. Through comparison of STRs, DNA technologies can confirm or deny blood relationships – an extremely valuable tool in scenarios such as missing person and disaster victim identification, lost-child and counter-human-trafficking applications, paternity and maternity testing, and determinations of eligibility for immigration benefits.
Advantages of DNA as a biometric:
- DNA is the only biometric that provides the possibility of linking relatives to an unknown person
- Like fingerprints, DNA is one of the few biometrics that can be “left behind”, like at a crime scene
- DNA testing is a relatively mature but dynamically evolving technology that is becoming widely used and is familiar to the public
- Rapid DNA identification devices are making positive identifications possible in as little as 90 minutes
- Ability to easily store large numbers of DNA results in databases increases the possibility of matches
- Standardized test chemistries and results file formats allow for interoperability between systems
- Well-known population statistics for human DNA markers provide high confidence in matching operations
- Advances in healthcare genomics offer promise that unknown (not in a database) forensic DNA samples can be characterized well enough to identify the owners