MEDICAL BAG
Genetic profiling was once hailed as a magical new tool to catch criminals, but DNA anomalies mean that its reliability is in question
DNA evidence in criminal trials and disputed paternity cases has come to be viewed as incontestable, perhaps as a result of the eventual conviction of two of Stephen Lawrence’s murderers, and of popular TV programmes like CSI: Crime Scene Investigation and the (now discredited) Jeremy Kyle Show. However, an increasing number of forensic investigators, lawyers and judges are beginning to raise concerns about the reliability of so-called genetic fingerprinting (aka DNA profiling) as evidence.
In 2012, David Butler, a former taxi driver from Liverpool, was put on trial for the murder of local sex worker Anne Marie Foy, found battered to death in woodland in 2005. DNA samples taken from under her fingernails were said to match that of Butler when searched against a police database following a ‘cold case’ review. His DNA was on the database because it had been extracted from a cigarette butt found during a 1998 police investigation at his mother’s house, following a burglary. Detectives had assumed the butt had been dropped by the burglar; in fact, Butler had left it during a visit to his mother to comfort her after the burglary.
The DNA taken from underneath Foy’s fingernails was the only evidence linking her to Butler, whose QC, Michael Wolkind, was scathing in his dismissal of the DNA evidence. Butler, he told the court, suffered from a dry skin condition so severe that his cabbie colleagues had nicknamed him ‘flaky’. It was entirely possible, suggested Wolkind, that after taking a fare to the red light district, Butler had given his passenger some change in the form of pound notes – covered in skin cells containing his DNA – which was then given to Foy.
Prof Allan Jamieson, a leading DNA forensic expert, was called for the defence. Jamieson, head of the Forensic Institute in Glasgow, has appeared at several high-profile criminal trials, most notably that of Sean Hoey, cleared of the 1998 Omagh bombing which killed 29 people. Jamieson, while a firm believer in DNA’s use as a powerful forensic tool, is concerned that police and prosecutors, incorrectly regarding DNA evidence as incontrovertible, have come to view it as a shortcut to conviction, a substitute for more time-consuming and costly investigation. He has warned of the dangers of human error, contamination and accidents leading to unjust convictions, with particular misgivings about the use of tiny amounts of DNA. Recent technological advances mean that what is known as Low Count DNA may now be extracted from two or three cells of a sample, rather than from hundreds or thousands.
“Does anyone realise how easy it is to leave a couple of cells of your DNA somewhere?” Jamieson said during an interview with the Daily Telegraph. “You could shake my hand and I could put that hand down hundreds of miles away and leave your cells behind”. After eight months on remand, David Butler was acquitted.
Further concerns about DNA’s reliability were raised when a US man, diagnosed with leukaemia in 2013 and recipient of a bone marrow transplant, learned that the DNA in his blood had changed to that of his donor, 5,000 miles away in Germany. Chris Long, of Reno, Nevada, was encouraged to test his own blood three months after the transplant by his friend and
Certain medical procedures can turn people into chimeras
colleague Renee Romero, based in the crime lab at Washoe County sheriff’s office. She had a hunch this could happen since the procedure itself entails the replacement of weak by healthy blood.
Four years after his lifesaving transplant, Long discovered that not only his blood had been affected. Swabs of his lips and cheeks were found to contain both his DNA and that of his donor, whilst all the DNA in his semen corresponded to his donor’s. “I thought that it was pretty incredible that I can disappear and someone else can appear,” Long said. He has become a chimera, the scientific term borrowed from the Greek mythological creature that was a composite of lion, goat and serpent. Doctors have long known that certain medical procedures can turn people into chimeras, but the implications for law enforcement hadn’t been considered – until now.
Each year, tens of thousands of people have bone marrow
transplants for blood cancers, leukaemia, lymphoma, sickle cell anaemia and other disorders. The likelihood of one or more of them becoming a perpetrator or victim of crime was unlikely but not impossible. So Long’s sheriff’s department have been using their IT colleague as a human guinea pig.
The implications of his case were presented at an international forensic science conference in September 2019. Crime scene investigators who gather DNA evidence were hitherto confident that each victim and each perpetrator leaves behind a single identifying code. Not any more.
This transplant oddity has already misled investigators. In 2004, Alaskan detectives investigating a sexual assault uploaded a DNA profile extracted from semen to a criminal DNA database, which matched a potential suspect. However, at the time of the assault, the man had been in prison. Further enquiries revealed that he had received a bone marrow transplant from his brother, who was eventually convicted of the crime.
Abirami Chidambaram, who worked on the case at Alaska’s state scientific crime detection laboratory in Anchorage, said she has since heard of another troubling DNA scenario. Detectives investigating a sexual assault were sceptical of the victim’s account because of her insistence that there had been one attacker, while DNA analysis indicated two. Eventually it was established that the second profile was that of her bone marrow donor.
In 2008, Yongbin Eom, a visiting research scholar at the University of North Texas Centre for Human Identification, was trying to establish the identity of a traffic accident victim in Seoul, South Korea. Blood tests showed the individual was female, but the body appeared to be that of a male. This was confirmed by DNA from the victim’s kidney, but the spleen and lung contained both male and female DNA. Eom eventually established that the unfortunate man had previously received a bone marrow transplant from his daughter.
Chris Long’s situation has raised an intriguing question – if he has a baby, will she or he inherit his own genes or that of his German donor? In this case, the question will remain unanswered, because Long had a vasectomy some time ago. Bone marrow transplants say it should be impossible for a parent to pass on someone else’s genes – but who knows? Fraternal twins sometimes acquire each other’s DNA while in the womb. In 2006, Lydia Fairchild of Washington state nearly had her children taken into custody after a DNA test suggested she wasn’t their mother. In fact, she had absorbed her own fraternal twin whilst in the womb; effectively, she was her own twin, so that her children acquired the fraternal twin’s DNA instead of hers. And in another case, suspicions of infidelity followed a DNA paternity test that indicated a man wasn’t the father of his own son. In fact, he, like Lydia Fairchild, had absorbed his fraternal twin before birth.
Experts say a donor’s blood cells should not be able to create new sperm cells, but this is just what happened to Long. A doctor who treated him believes Long’s vasectomy somehow caused his semen to contain his donor’s DNA, but this is just a supposition, and further investigation is planned.
As for Chris Long, he is planning a trip to Germany, where he hopes to meet his donor in person and thank him for saving his life. liverpoolecho.co.uk, 11 Feb; D.Telegraph magazine, 4 April 2012; time.com, 28 Oct 2015; independent.co.uk, 9 Dec; mynews4.com, 21 Dec 2019.