What can DNA tell you about a crime?
The scene is set in a generic crime lab, lit in soft blue with scientific equipment sitting side by side with a mortuary table. The tense music builds as a montage of the technician alternately swabbing the murder victim, peering down a microscope, or running a centrifuge, scrolls across the screen. Finally, the key suspect is exonerated and the unlikely murderer unmasked, and it all comes down to a speck of DNA.
Crime dramas are an entertainment staple across the world. But as DNA becomes a more powerful tool for identifying the guilty, exonerating the innocent, and building a successful criminal case it is essential, argues UK charity Sense About Science, that public and professional expectations of the technology are based in reality and not TV crime fiction.
Which is why the organisation has published a new guide called Making Sense of Forensic Genetics, which challenges unrealistic perceptions of DNA evidence, and explains where the big differences between reality and fiction lie.
For example, your DNA is found at a crime scene. How did it get there? In CSI or Law and Order, that would immediately imply guilt. But in reality we all shed DNA into our environments all the time, through skin cells, and hair, and saliva, and you would be surprised just where that DNA can end up.
Making Sense of Forensic Genetics explores several examples of wrong DNA identified at the scene, including the case of taxi driver David Butler. His DNA was recovered from the fingernails of murdered sex worker Anne Marie Foy, in what seemed like an open and shut case. It was presumed that Ms Foy had torn at his skin as he hit and strangled her, before dumping her body in a Liverpool park in 2005. However, his defence team established that some of his skin cells had transferred on to bank notes that were later used to pay Ms Foy.
Outside of the crime scene, this guide throws up some key questions that are relevant to DNA sequencing and DNA data as a whole. One is the increasing ability to predict appearance and ancestry from DNA. While the technique is by no means 100% accurate, the level of detail it can already give is alarming. In a recent interview for WIRED, genomicist Craig Venter revealed the extent to which Human Longevity can predict individual characteristics from bare genetic code.
“From just the fingerprint on your pen, we can sequence your genome and identify how you look,” Venter explained. “It’s good enough to pick someone out of a ten-person line-up and it’s getting better all the time.”
How can we protect individual data privacy in genetic databases when we can reconstruct a face from an unwittingly shed piece of DNA? Data privacy is just as critical a topic for forensics as it is for health databases, but some of the issues are reversed. In a genomic health database, participants consent to their data being included and distributed for research. For criminal databases, DNA is not willingly given, but collected during the forensic process. Should governments have the right to hold the DNA of people without criminal conviction indefinitely? According to Making Sense of Forensic Genetics: “Some people have argued that if everyone in a country were held on a national DNA database, far more crimes would be solved, but many are opposed to this idea on the grounds of personal privacy and human dignity.”
As 2017 could well be the year that we welcome Jennifer Lopez on to our screens in C.R.I.S.P.R, a crime drama in which gene editing takes centre stage as the “next generation of terror” (think “genetic assassination attempts” on the life of the president, and framing an unborn child for murder), we could all do with reminding ourselves where the boundaries between reality and Law and Order sit.