Police looking to identify an unknown suspect often rely upon a technique called criminal profiling in hopes of gaining some potential insight into their psychologies. But now a new forensic technique called Hirisplex could soon allow investigators to take this process a step further by allowing them to predict certain physical characteristics of suspects — like their hair and eye color — after analyzing traces of DNA that were left at the crime scene.
The field of Forensic DNA Phenotyping (FDP) has started to take root in forensic biology — a set of techniques that are increasingly allowing police investigators to drastically narrow down a large group of possible suspects.
DNA analysis is not new to forensics. Unlike genetic profiling, which takes a fingerprint-like approach to investigations, FDP does not require any pre-exiting information about an alleged criminal. In genetic profiling, a pre-existing database of DNA is cross-referenced against new evidence left at a crime scene. The obvious shortcoming of this approach is that, like a fingerprint, the database has to contain the suspect's DNA in order to make a match.
The Hirisplex system, on the other hand, can make predictions about a suspect's physical profile from scratch.
Paul Rincon of the BBC explains how it works:
The test system includes the six DNA markers previously used in a test for eye colour known as Irisplex, combining them with predictive markers for hair.
In the study, the authors used Hirisplex to predict hair colour phenotypes in a sample drawn from three European populations.
On average, their prediction accuracy was 69.5% for blonde hair, 78.5% for brown, 80% for red and 87.5% for black hair colour.
Analysis on worldwide DNA samples suggested the results were similar regardless of a person's geographic ancestry.
The team was also able to determine, with a prediction accuracy of about 86%, whether a brown-eyed, black haired person was of non-European versus European origin (excluding some nearby areas such as the Middle East).
The study was published in FSI Genetics and can be found here.
Top image via PeterPhoto123/Shutterstock.com.