Is DNA profiling a truth machine or a gold standard? I always used to believe it to be so. Could there be anomalies? In 1998, two men abducted a woman at gunpoint, then raped her and tossed her into a nearby field. Five days after the attack, the victim while driving into her neighbourhood, recognised two men as her attackers. One of them was Josiah Sutton. The two identified teen boys made consent to the police to lend their blood, and saliva samples for comparison with the evidence gathered from the victim and their car. The DNA testing concluded that Sutton might have been an attacker but excluded his friend as the lab results found the semen sample recovered from the backseat of the car matching with the profile of Sutton and another unknown man. Despite the victim identifying both the boys, the police put only Sutton to trial. During the prosecution, a lab technician deposed that DNA found on the victim was a precise match of Sutton. Court awarded Sutton a 25-year sentence for the offence of rape, although he asserted his innocence during the trial that he did not commit the crime. Sutton's requests for an independent DNA test met with rejection from the authorities, but an independent investigation of the police crime laboratory unveiled the truth. Fast forward to 2004; court exonerated Josiah Sutton after serving four and a half years of a 25-year sentence. Sutton’s conviction had stemmed from erroneous identification and faulty scientific testing conducted by the Houston police laboratory.
Although DNA tests are thus credible when compared to other forms of evidence, those DNA tests have never been foolproof. When DNA testing came into being, several experts asserted that false positives could never happen in forensic DNA testing. Such contentions are ominous and misleading because humans perform DNA tests, and they can make errors while conducting tests. There are several instances where DNA evidence has resulted in erroneous incriminations and false convictions. Authorities have reported false incriminations because of faulty DNA testing, inadvertent or an accidental transfer of cellular material or DNA from one sample to another, as well as coincidental DNA profile matches between different people, errors in identification or labelling of specimens, misinterpretation of test results, and purposeful planting of biological evidence.
In Josiah Sutton’s case, wrong conviction came about partly because of DNA testing errors. A combination of technical issues in the lab and inaccurate or erroneous interpretation of the test results-producing misleading DNA evidence had sent innocent Sutton to prison for many years.
DNA technology of late has become more sensitive, turning it into a double-edged sword as it can now detect and analyse DNA from samples comprising only 16 cells. But because of the touch-transfer properties of DNA, deducing how those cells arrive at the surface on which they are found is impossible. Small amounts of touch-transferred DNA have placed people at locations they had never before visited and implicated people for crimes, they did not commit.
Someone whose DNA is available at the crime scene could have got deposited before the crime took place or after the commission of the crime. There is also the possibility of DNA entering the scene by a process called secondary transfer, where the DNA of a person could get disseminated to another person who could carry it and leave behind at the stage. Detection of DNA that came by contamination and DNA that came by secondary transfer has become possible baffling investigations. If we don't train the forensic and legal experts to deduce forensic evidence, it could grossly lead to a miscarriage of justice.
For instance, in December 2012, police arrested Lukis Anderson and charged him with the murder of Raveesh Kumra a Silicon Valley multimillionaire. Police had found traces of Anderson's DNA on the fingernails of the deceased millionaire. Police based on the presence of Anderson’s DNA on the millionaire and his voluble criminal record surmised that he could be the murderer. Not knowing what had happened on the night of high drunkenness, Anderson accepted before the police that he might have perpetrated the murder under the state of high intoxication. But after five months in jail police released Anderson from prison as their investigation disclosed that Anderson had been drunk and nearly comatose, hospitalised, under constant medical supervision, on the night of the murder.
Police later also found out that the doctors who had treated Anderson had by accident caused the transfer of Anderson’s DNA to the deceased millionaire when they had to respond to the crime scene at Kumra's residence a few hours later. Anderson was therefore a victim of touch-transfer DNA misinformation.
Another difficulty with DNA is that people slough DNA at different rates. We find DNA in bodily fluids, such as blood, semen, and saliva, but we also lose microscopic pieces of skin and hair regularly. The ability of people to lose DNA varies from individual to individual. Some individuals have a skin condition such as eczema, which makes them lose more skin cells than others. If a burglar opens a vault and commits theft of valuables and if the inmate of the house inspects it to assess the extent of loss, the quantity of DNA left behind by the inmate would suggest that the reported crime is not a true case. As the quantity of DNA left by the dweller would be so enormous that it would become difficult for the forensics to implicate the burglar.
On a beautiful November morning, Merseyside Police woke David Butler, a retired taxi driver by knocking on his door. They told him they were arresting him for murder as they had evidence connecting him to the death of Anne Marie Foy, a 46-year-old sex worker found battered and strangled by police in Liverpool in 2005. It so turned out that Butlers DNA was available on the National database and the police had found a partial match to DNA found on Foy's fingernail clippings and cardigan buttons. This together with CCTV evidence of unique taxi provided compelling evidence of his complicity in the crime. But Butler was adamant that he had not met Foy. The defence during the trial argued that Butler had a disposition of flaky skin which sheds more cells and Foy was wearing nail polish which keeps DNA for a longer time therefore Butler's DNA had got to the victim by innocent means. This evidence, consequently earned him an acquittal after eight months in remand.
Wrong DNA matches in several cases have also resulted in several wrongful convictions. One cause of false DNA matches is because of the cross-contamination of samples. Random transfer of cellular material or DNA from one sample to another is a serious problem in laboratories leading to false reports of a DNA match between samples that emanated from different people. Besides, accidental cross-contamination of DNA samples has also caused several erroneous “cold hits.”
In 2011, police implicated Adam Scott, who lived 200 miles away and never visited Manchester in a rape of a Manchester woman based on DNA match with the sperm sample collected from the victim. All because, the lab which was analysing Scott's DNA in a minor incident ended up reusing the same sample by accident for the rape case. Non-DNA evidence however cleared Scott.
It is often ambiguous when samples of trace DNA from skin cells, semen or other body fluids, contains DNA from many individuals which are hard to differentiate.
Also, finding out the time when the DNA might have got inserted and the time since when the DNA has got plopped is an enormous problem. For instance, if the victim was wearing clothing, and if the clothing contained a mixed profile it would be difficult to determine whether the major profile belongs to the last person who wore it or somebody who wore the clothing regularly. Studies from several groups have looked at several factors influencing how much DNA people leave behind. Such things as how long it was since somebody washed their hands and which hand of a person touched an object can affect the amount of DNA left behind.
In 2013, Michael Coble of the National Institute of Standards and Technology in Gaithersburg, Maryland, USA concocted a scenario of a finding a criminals ski mask who had committed a series of crimes at a crime scene with a mix of DNA from several people. Coble requested 108 labs across the USA to discern whether a DNA sample that came from a suspect was also part of the mix.
Seventy-three labs out of the 108 labs didn't get it right; They found suspect DNA to be part of the mix when in fact it was not. We therefore leave too much to the discretion of the labs.
We should not oversell DNA evidence. Courts should take the standards of the lab into reference before considering DNA evidence. Misuse of DNA leads to a miscarriage of justice. Based on a partial DNA match, the courts handed a man afflicted with Parkinson's disease with little ability to walk a conviction for the crime of burglary. But his lawyer’s insistence on more tests eventually led to his exoneration.
Criminals have become smarter and have learnt the art of evading crime control technologies. Criminals have now learnt to plant biological evidence. Deliberate planting of DNA may cause a substantial risk of false incriminations. When such planting of DNA evidence takes place, will the police be able to uncover it? Will the courts believe that a defendant is innocent when there is a DNA match?
Finally, is the DNA test foolproof? Assertions are being made that the dependability and validity of DNA is never in doubt. Public belief in the technique that it is a truth machine a gold standard is being further bolstered by news of post conviction exonerations where release of wrongly sentenced persons is being shown on TV and media. The magniloquence of infallibility has led to the admissibility of forensic DNA tests as a testimony in courts. This has also caused the advancement of government databases. One indication of the success and influence of the rhetoric of infallibility is that, until recently, worries about wrong incriminations played almost no role in discussions about database expansion.
The hazard of untrue incrimination should make us seriously ponder over expansion of databases. India recently passed the DNA Technology (Use and Application) Regulation Bill, 2018, which envisages DNA databases. It is a known fact that people whose profile is in DNA database are at a higher risk of incriminations than other citizens of being falsely linked to a crime. Today, DNA singly is no longer considered being an adequate proof that a particular person certainly committed a crime. It’s often used as supporting evidence, and the days of DNA being a “smoking gun” or “bullet proof “ are already over.
