Using DNA evidence to picture suspects

While forensic scientists first used DNA to confirm a suspect in the 1980s, they needed a suspect to begin with. They could compare the suspect’s DNA with their forensic sample. Now, forensic scientists can exploit how DNA shapes who we are.

In the 1990s, forensic scientists mainly focused on characteristic short tandem repeat (STR) sections of human DNA that change a lot between people. This technique still dominates forensic DNA analysis. STR-based DNA profiling can confidently identify an individual based on a match between a sample known to be theirs and one from a crime scene. STR sequences usually don’t tell investigators anything else about the suspect though, so DNA profiling is no use if you can’t link someone known to crime scene samples. Therefore, scientists have turned to forensic DNA phenotyping (FDP).

FDP can predict some external appearance traits. Eye, skin, and hair colour are easiest to identify: they’re associated with genes that control how we make pigment molecules known as melanins across many types of tissue.