The Case of Genetic Leftovers
“If you’ve ever handled a penny, the government’s got your DNA. Why do you think they keep them in circulation?” — The Simpsons
When you pay the bill, it seems like the only additional thing you leave behind is a tip. Little do you know that you’ve left enough genetic material to send off for a 23andMe test. Piecing together the handshakes, the cigarette butts, saliva on the cutlery and more, anyone with the now readily-available technology can identify you.
Take the Grim Sleeper case: a southern Californian serial killer who terrorised women from 1985 to 2007. In a pizzeria in Los Angeles, a policeman disguised as a staff member took the utensils, plates, and pizza crusts a customer left behind to a forensics lab. From this ‘abandoned’ DNA, they identified the customer as Lonnie David Franklin Jr. — the Grim Sleeper.
Thanks to this success and many more, law enforcement agencies look to restaurants and other public places as prime sources for usable genetic material — abandoned DNA. This term refers to any quantity of human material left behind involuntarily or inadvertently that is stable enough for DNA analysis.
Surely this is illegal, you might think.
Non-consensual DNA testing was outlawed in the UK in 2006, whereas the US has failed to pass similar legislation. Previous legal cases have shown some police to “act as passive collectors, waiting for a suspect to discard a smoked cigarette or to spit on the floor”. There is no regulation to prevent any law enforcement official from taking advantage of abandoned DNA. In fact, during People v. Ayler in 2004, the judge denied the suppression of incriminating DNA evidence obtained from cigarettes offered to the defendant in a police interview.
This fear of your own DNA betraying you has reached those at the top of society. It has been said that the Secret Service collects the cutlery and tableware the US President uses when on tour. Even Madonna has a personal sterilisation team, deep-cleaning her dressing rooms to rid them of ‘leftovers’.
But, is DNA profiling even accurate?
Heather Dewey-Hagborg’s art suggests so. Her 2012 ‘Stranger Visions’ project comprises portrait sculptures from analyses of genetic material collected in public places. With the help of unknowing strangers’ abandoned DNA, she shares a glimpse of a future of genetic surveillance, highlighting issues of privacy and bioethics. From just a strand of hair, an entire facial sculpture is created.
So, it makes sense that DNA profiling has always been seen as the infallible forensic technique that would solve crimes. However, what does it really tell us about crime? With its incredibly high rate of transfer, matching DNA samples are not strong enough to prove guilt. In 2012, Lukis Anderson was betrayed by his own DNA as he was convicted for murder. His DNA was found at the crime scene, implicating him immediately. It was considered valid evidence and was used against him in court, but it was only after his public defender detailed his robust alibi that they concluded Anderson was not there.
Despite the inconsistencies in DNA profiling, the current tendency is to elevate genetic data above equally crucial contextual evidence. The first step in collecting genetic evidence is knowing which areas and surfaces to find it. But, current approaches are blighted by inaccuracies, as low-quality DNA is often collected. Next comes extraction. Despite improvements over the years, many tracing kits lose up to 75% of the DNA present found in the sample. Once extracted, the DNA sample is amplified through polymerase chain reaction (PCR) and repetitive sequences called short tandem repeats are analysed. But, this endeavour is often fruitless since contamination is a huge issue.
These nuances of DNA profiling aren’t clarified in courtrooms; juries are told that genetic material never lies, which we know is not the case. It is crucial that we view DNA profiles in their context.
The journey of DNA in the legal world has always been a messy one. Until it cleans up, try to make sure to take your genetic leftovers with you.
Originally published in UCL Kinesis Magazine Issue 7 on January 28, 2021.
Editor: Andrey Chau
