(Originally published on Occam’s Corner at Guardian Science, in February 2017)
Advances in epigenetics mean incredibly detailed profiles of criminal suspects might soon be reality. Is the legal system ready to use this information?
Picture the scene. A detective is addressing her team:
“The DNA test results are in. We’re looking for a white male suspect, 34–37 years old, born in the summer in a temperate climate. He’s used cocaine in the past. His mother smoked, but he doesn’t. He drinks heavily, like his Dad. We’re seeing high stress levels, and looking at the air pollution markers, let’s start looking downtown, probably near a major intersection”.
Science fiction? Yes, for now. But advances in epigenetics – the study of reversible chemical modifications to chromosomes that play a role in determining which genes are activated in which cells – might soon start making their way out of research labs and into criminal forensics facilities.
Take the idea of the epigenetic clock, one of the ways in which our cells and DNA can betray our age. Epigenetic patterns change throughout our lives, along broadly predictable paths, making it possible to infer age from DNA samples.
Steve Horvath at UCLA has developed a statistical model based on 350 potential epigenetic modification positions in the human genome that can estimate your age to within three and a half years. The rate of epigenetic aging seems to depend somewhat on race, and can be affected by some health conditions, but this kind of test is already at the stage when forensics labs are validating it for use in criminal investigations.
The things we get up to while our epigenetic clocks are ticking can also leave their mark on our DNA. Cigarette smoking correlates with characteristic and persistent epigenetic changes. The same goes for cocaine, opioids and other illicit substances. There’s also some evidence for epigenetic signatures of obesity, traumatic childhood experiences, exposure to tobacco in the womb, season of birth, exposure to environmental pollution, exercise, and possibly even the things our parents and grandparents did before we were born.