This is How DNA Evidence Goes Wrong

hey 42 here in 1998 in Houston a 41 year old woman was abducted at gunpoint from the parking lot of her apartment complex the kidnappers took turns in raping her a few days later the woman spotted two men a similar age walking down the street as she drove around her neighborhood the men she suspected were Josiah Sutton aged 16 and Gregory Adams 19 they were arrested but after intense questioning it would seem as though the victim had been mistaken the two men had solid alibis which placed them elsewhere at the time of the rape furthermore the victim initially described the assailants as short and skinny yet Adams and Sutton were both tall well-built and stocky the police requested blood and saliva samples from both men so that they could definitively rule them out via DNA testing because DNA analysis is infallible right the boys were within their rights to say no but why would they both knew they had no part in the rape and were more than happy to clear their names they agreed the samples were sent to the Houston Police Crime Lab to be compared against the DNA from a semen sample retrieved from the scene of the rape it was a match the results strongly indicated that Josiah Sutton had been the perpetrator of the rain but they excluded Adams as a suspect Josiah Sutton was sentenced to 25 years in prison for a rape he did not commit but how do we know he didn't well after four years of incarceration Sutton's mother who always believed his pleas of innocence because of a small fact that she was actually with him at the time he supposedly committed the rape was watching TV when a report aired it was a peace dismantling the integrity of the Houston Crime Laboratory that had handled Sutton's DNA and that of over 500 other suspected criminals each year it revealed how Houston crime lab technicians and processes were woefully inadequate and often wrongly interpreted DNA test results Sutton's mother contacted the reporters and they arranged for her son's DNA to be retested by another lab the results were as clear as day so since DNA did not match that taken from the scene of the rape and there was no way it could have ever been misconstrued as a match unless there was extreme negligence after spending four years inside Sutton was exonerated and regains the freedom that was stolen from him due to the police relying on nothing more than a single piece of DNA evidence that was never cross verified for validity and ultimately proved to be wrong Watson and Crick first discovered DNA in the 50s but it wouldn't be until 1986 when dr. Jeffries used DNA for the first time as evidence in a criminal investigation before the widespread adoption of DNA analysis the go chief forensics tool was hair analysis lab technicians would compare hairs found at the crime scene we've not taken from a suspect under an electron microscope based on the color pattern and over telling patterns within their hair strands a conclusion could be reached on whether or not the two strands matched indicating the incriminating hair belonged to the suspect in question countless people around the world have been incarcerated as a result of this technique but hair analysis has been superseded by DNA which is unquestionably more accurate and reliable hair analysis is actually still used by law enforcement but usually as a way to rapidly exclude potential suspects without having to wait for DNA results hair analysis is no longer considered to be reliable evidence in court in fact over the past 20 years it has come to light as an over-reliance on hair analysis up to the 90s resources in the wrongful convictions of potentially thousands of innocent people a non-profit the Innocence Project was established in 1992 to come to the aid of such people and work on their behalf to clear their names and set them free often using more up-to-date forensic techniques such as DNA analysis as of 2019 the Innocence Project has used DNA to exonerate 189 people most of whom were originally convicted based on her analysis so don't get me wrong DNA analysis is incredible it is by far the most accurate and reliable form of criminal evidence we have it's often touted as being over 99.9% accurate it is a scientific marvel that has helped catch thousands of rapists murderers and other criminals and prevented thousands of innocent people from being wrongfully convicted but like anything it's still not perfect and a lot more often than you may think DNA gets it terribly wrong and I'm about to tell you exactly how and why that can happen almost always when DNA evidence is incorrect it is not due to the DNA analysis technology itself it is due to human error first start the DNA evidence can be collected incorrectly at the crime scene crime scene investigators are usually extremely well-trained to mitigate any errors or causes for confusion over crime scene samples and by enlarge as they take the greatest care and due diligence in their jobs after all there was usually a person's freedom at stake yet mistakes do happen more often than you might think at a typical crime scene there are usually many opportunities to take DNA samples from strands of hair and blood splatters to saliva and semen sweat samples can even be collected from materials such as pieces of clothing or bed sheets the issue is tough it's extremely rare that any crimes only contains DNA evidence from two persons the victim and the perpetrator an average room is not even close to being completely sterile and they will usually be objects containing DNA from visitors to the house or there could be external DNA upon objects that have been brought into the home it's any point in the recent past and this problem is many times worse when a crime scene is outside or in a public space imagine if a murder takes place in an underground tube station there will be DNA from thousands of individuals and it is the considerably difficult job of forensics to find that single piece of DNA amongst it all that is the most pertinent to solving that case DNA is often forced off as an emotionless entirely formulaic form of evidence but the reality is quite different there is much more human emotion and decision-making involved than is ideal there are actually many points along the DNA evidence pipeline where a human element is introduced deciding which samples from the crime scene are actually relevant to the case is one such point which is almost entirely based on human decision-making rather than cold hard scientific fact and unfortunately humans are infamously indecisive and inconsistent to make matters worse most of the time DNA samples are mixed together if two or more people have touched the same object or worn the same item of clothing than any DNA samples extracted will most likely be a mix of those two persons this means they have to be teased apart later in the laboratory which is difficult and prone to red herrings and almost always at any crime scene the criminals DNA whether it's from skin cells sweat or blood is going to be mixed with that of victims the more violent and prolonged the crime than the more likely that mixed DNA samples are going to be an issue and then there's the other issue of partial DNA samples attempts to clean up the crime scene by the perpetrator afterwards or something as simple as him washing his hands can cause him to leave only partial DNA samples which can throw the most experienced lab technicians off the scent even causing mismatches with the DNA against a complete stranger who was never at the crime scene but may now be wrongfully arrested when the DNA samples do reach the lab yet another human element is thrown into the mix to dilute the reliability of what should be in an ideal world a purely scientific method I'm talking about basic human bias the most commonly used forensic method for comparing DNA samples is called DNA profiling this allows a hugely complex of DNA code to be boiled down to a series of grafts on a single sheet of paper think of each vertical bump here as being a unique DNA signal like a section of your fingerprint the height of the bump signifies how strong that piece of DNA was in the sample by comparing two such graphs from two distinct samples say one taken from a strand of hair found at the crime scene and the other from a strand of hair belonging to the primary suspect the forensic scientist can make a decision on whether or not they think this is a match and it is hence the same person at first it seems like a relatively simple task with little room for error but that's only true when samples are cleaned and complete which for various reasons that we talked about only a couple of minutes ago they almost never are partial or weak samples of DNA produce what's called noise on DNA profiles noisy sections can appear to be highly indeterminate and a human decision must be made at this point whether it is meaningless noise or simply a weak DNA signal what's a signal nevertheless this can be the difference between a lab technician deciding that two samples do in fact much or do not match which can be the difference between guilty and not guilty these fringe scenarios often rely on nothing more than the bias of the examiner and this bias can often be intensified because in most countries including the US DNA samples are often labeled and so the lab technician knows who it belongs to if they already suspected the jealous ex-boyfriend of committing the murder and the difference between a positive DNA match and a negative is only a tiny little piece of noise on the DNA profile then the lab technician might opt to declare it a match in his report whereas if the samples were instead tested blindly ie the technician did not know the identity of the person from whom the DNA was sourced then his decision may have been more pragmatic and less emotional and he thus may have instead concluded that there was no match in 1993 in either Oberstein Germany a 63 year old woman was murdered in her home forensics discovered mysterious DNA on a cop in her home the DNA belonged to a female but apart from that that police had no idea whose it was then again in 2001 a 61 year old man was murdered in Freiburg Germany the very same DNA was found on a kitchen drawer than what was recovered in 1993 the police immediately suspected that they could have a serial killer case on their hands but since the DNA wasn't on the police database all they could do was wait until she struck again and hopefully made and the take the media branded the serial killer the Phantom of Heilbronn others called her the woman without a face over the next eight years the police would discover the Phantom woman's DNA at the scene of 40 crimes all over Germany Austria and France including murders and burglaries but it didn't matter how often the Phantom of Heilbronn struck or how many times her DNA was recovered and analyzed the police had no leads as to her identity that was until 2019 when there was a break it was discovered that a female worker at a factory had inadvertently contaminated several batches of cotton swabs and these has happened to be the same swabs that many German French and Austrian forensics teams used to collect DNA evidence at crime scenes the mystery had finally been solved there was no serial killer all 40 crimes were completely related the only link between them was the DNA which was originating from the contaminated cotton swabs the police were able to confirm this because Bavaria although being situated directly in the center of all of these crimes had no Phantom of Heilbronn DNA matches and why was that because the Bavarian CSI unit ordered their cotton swabs from a different factory thanks for watching if you enjoyed this video then please consider supporting me on patreon which really helps me to continue making these videos also I've recently launched my first book sticker flag in it a thousand years of bizarre history from Britain and beyond you can get your hands on a first edition signed copy by clicking the link in a description and heading over to unbound publishing thank you

Channel: Thoughty2

Views: 146,482

Rating: 4.9582343 out of 5

Keywords: dna, evidence, crime, csi, police, investigation, crime scene, crime scene investigation, true crime, crime documentary, crime documentaries, factual, thoughty2, criminal investigation, forensics, police investigation, crime scene analysis, forensic science, crime scene reaction, forensics science, forensic, analysis, forensic files, forensic psychology, cold case files, murder, detective, truth, thouthy 2, the truth

Id: zszJ9JIzmV8

Length: 14min 58sec (898 seconds)

Published: Wed Mar 04 2020