Cold cases are crimes that have remained unsolved for long periods, often due to a lack of evidence, witnesses, or suspects. However, in recent years, advances in DNA technology have enabled investigators to identify the perpetrators of murders, rapes, and other violent crimes that had remained unsolved for decades.
Below, we’ve taken a closer look at how DNA technology works, what challenges it faces, and what implications it has for the future of criminal justice.
We’ve also pulled together a list of five of the UK’s most notorious cold cases that were solved using DNA evidence – such as Operation Minstead and the Cato Road Murders – bringing the criminals to justice.
Trigger warning: This article is for informative purposes only and is not intended to glorify tragic events, or make light of them. Although true crime cases can provide helpful insight into the human psyche and criminal legal system, we also appreciate that exposure to topics relating to violence and death can be distressing for some people. Therefore, reader discretion is advised.
Our thoughts go out to the victims, families, and anyone else affected by these – or similar – events.
How has DNA evidence advanced since its first use in 1986?
DNA evidence is when scientists use DNA to identify people or animals – helping to solve crimes, find relatives, or learn about health and ancestry.
In criminal investigations, DNA evidence is most valuable in confirming a victim or witness’ testimony or placing an individual at a crime scene. Because no two people have the same DNA, this evidence can be instrumental in proving someone’s guilt or innocence – though, of course, it does have some limitations, which we’ll cover later.
DNA evidence was first used to solve a crime that took place in England in 1986. Police asked Dr Alec J. Jeffreys from the University of Leicester, to verify a suspect’s confession that he was responsible for the rape and murder of two young girls. The resulting fingerprint tests proved that the suspect hadn’t committed the crimes.
Since then, DNA technology has continued to evolve because scientists have developed new ways to collect, analyse, and use DNA, making evidence more accurate and easier to obtain. Some of the most notable advancements in DNA technology include…
Massively parallel sequencing (MPS)
MPS is a technique that can read many DNA letters at once, very quickly and accurately. This makes it easier to analyse DNA from small or degraded samples (such as human remains).
It can also be used to read different types of markers, such as STRs, SNPs, or RNA. Markers are parts of the DNA that vary a lot between people and can, therefore, be used to tell individuals apart or find out if they’re related.
Probabilistic genotyping methods
Probabilistic genotyping methods can calculate the probability of different scenarios for the DNA evidence, such as how many people contributed to the sample, what their possible genotypes are, and how likely they are to match the suspect or the database.
These methods can deal with complex situations, such as when the DNA is mixed from more than one person, or when some of the DNA letters are missing or unclear due to degradation or contamination.
This is a technique that can identify the type of body fluid that the DNA came from, such as blood, saliva, semen, or vaginal secretions.
RNA profiling can provide more information about the source and context of the DNA evidence, such as the nature of the crime, the time of the crime, or the relationship between the victim and the suspect.
SNP phenotyping can predict some of the physical characteristics of the person who left the DNA, such as eye, hair, skin colour, facial shape, and biogeographical ancestry. This can help narrow down the pool of potential suspects, especially when there’s no match in the database or the suspect is unknown.
DNA methylation analysis
DNA methylation can measure the level of methylation in the DNA. Methylation is a chemical modification that affects how the DNA is used by the cell – and it can vary depending on the type of tissue and the age of the person.
This method can help determine the origin and timing of the DNA evidence, such as whether it came from blood or skin cells, and how old the person was when they left the DNA.
Forensic genetic genealogy
Forensic genetic genealogy uses DNA databases and genealogical records to trace the family tree of the person who left the DNA. This can help identify distant relatives or even the person themselves, by finding matches in the databases and following the links between them.
What are some of the challenges of DNA evidence?
DNA evidence is a powerful tool for identifying suspects and solving crimes, but it also has some limitations and challenges.
For example, DNA evidence can…
- Be contaminated, degraded, or mixed with other sources, making it difficult to obtain a clear and reliable profile.
- Be misinterpreted, manipulated, or fabricated by human error or fraud, leading to false or misleading conclusions.
- Raise ethical and legal issues, such as privacy, consent, discrimination, and access to databases, that need to be addressed and regulated.
- Create unrealistic expectations or overconfidence among jurors, lawyers, and judges, who may rely too much on it or ignore other types of evidence.
These challenges mean that DNA evidence is not a magic bullet that can solve all crimes or prove guilt or innocence beyond doubt. It’s one piece of the puzzle that needs to be carefully collected, analysed, and presented in the context of the whole case.
It also means that forensic science and criminal justice need to constantly improve their standards, methods, and practices to ensure the quality, validity, and integrity of DNA evidence.
Having said that, DNA evidence has been groundbreaking in solving some of the most perplexing cold cases of the last century. Here’s our roundup of five of them.
5 cold case murders solved by DNA evidence
1. The rape and murder of Lynda Mann and Dawn Ashworth
Colin Pitchfork was 22 years old when he raped and murdered two 15-year-old girls. Pitchfork – who was married, with two sons – raped and strangled Lynda Mann in 1983 in the Leicestershire village of Narborough as she walked home from a babysitting job. His baby son was asleep in the car.
In July 1986, Dawn Ashworth was also brutally killed in a similar attack in the neighbouring village of Enderby, less than a mile from where Lynda died.
The investigating police officers initially arrested a local teenager, Richard Buckland, who confessed to killing Dawn but denied killing Lynda. The police decided to use DNA profiling to prove his guilt – but, to their surprise, the DNA didn’t match and Buckland became the first suspect cleared by DNA profiling.
The police then launched a massive screening of 5,000 men in the area, asking them to provide blood samples for DNA testing. Pitchfork, however, managed to evade the test by asking a friend to give a sample on his behalf. He was eventually exposed by a colleague who overheard him bragging about his deception.
The police arrested Pitchfork and his DNA matched the killer’s. He pleaded guilty to both murders and was sentenced to life imprisonment in 1988. The case was groundbreaking, as Pitchfork became the first person to be convicted of these crimes using DNA profiling.
2. The rape and murder of Marion Crofts
Marion Crofts was a 14-year-old schoolgirl who was raped and murdered in Aldershot on June 6, 1981. She was cycling to a clarinet lesson when she was attacked by a man near a canal. Her body was found in the bushes and her clarinet case was thrown into the water. The killer left traces of his DNA on her body and clothing, but the police couldn’t identify him at the time.
The case remained unsolved for 21 years until advances in DNA testing enabled the police to obtain a full DNA profile of the killer in 1999, using the semen found on Marion’s left sock and jeans, which had been partially pulled off. The police entered the profile into the national DNA database, but, unfortunately, there were no matches.
However, in 2001, a former soldier named Tony Jasinskyj was arrested for assaulting his wife in Leicester. He was swabbed for DNA and his profile matched the one from Marion’s murder. The jury was told that the DNA match to Jasinskyj was one in a billion.
Jasinskyj had been stationed in Aldershot in 1981 and had lied about his whereabouts on the day of the murder. He denied killing Marion and claimed his DNA had been planted at the crime scene. But, because of the presence of his DNA at the crime scene, he was convicted of rape and murder in 2002, and sentenced to life in prison.
3. Operation Minstead
Delroy Grant was a serial rapist and burglar who is feared to have targeted more than 1,000 people aged between 68 and 89 in south London, Kent, and Surrey over two decades. Grant was dubbed the ‘Night Stalker’ by the media and the police because he carried out his heinous crimes in the dead of night – targeting women who lived alone. He often gained entry through open windows which he sometimes removed entirely.
One of the reasons that Grant went undetected between 1992 and 2008 was because of his forensic awareness. He never left a fingerprint at the scene of a crime and covered a wide area, so the randomness of his crimes was difficult to predict. He would also stalk his victims beforehand to get familiar with their movements and property.
Grant was known as a charismatic man who cared for his disabled ex-wife so his societal profile wasn’t one you might not necessarily connect to such despicable crimes. But, he was finally caught in 2009, when DNA was collected from 10 of the crime scenes – mostly from pensioners who agreed to undergo medical examinations after being raped by the former minicab driver.
However, when confronted with such evidence, rather than admit to his crimes, Grant resorted to a series of increasingly bizarre legal defences. He claimed he was framed by his ex-wife, who had access to his DNA, or by corrupt police officers, who planted his DNA at the crime scenes. He also suggested that his DNA was contaminated by a rare genetic condition that made him share DNA with other people.
None of these defences were accepted by the jury who convicted him of 29 offences, including rape, indecent assault and burglary, in 2011. He was sentenced to life in prison with a minimum of 27 years. The judge described him as a “very evil man” and one of the most dangerous men in the country.
The case is notable for the long delay in justice and the role of DNA evidence in solving a cold case. The police missed a chance to catch Grant in 1999 when they mistakenly eliminated him from their list of suspects due to a clerical error. As a result, he was able to continue his attacks for another 10 years, during which he committed 146 more offences, including 23 sexual assaults.
Operation Minestead was also the basis for an ITV drama, Manhunt II: The Night Stalker, starring Martin Clumes.
4. The Cato Road Murders
William Danso and Patrick Dunne were both shot dead in Cato Road, Clapham, south London, on October 20, 1993. Danso, 31, had two disputes that day with Gary Nelson, one of Britain’s most dangerous gangsters – one at a mobile phone shop where he worked as a security guard, and another while working as a bouncer at a nightclub where he refused Nelson access.
Later that night, Nelson, 36, and two others arrived at Danso’s flat, armed with a 9mm semi-automatic and an Italian-made Tanfoglio self-loading pistol and shot the father-of-four dead.
PC Dunne, 44, was an unarmed police officer who arrived at the scene by chance after tending to a domestic dispute in the house opposite. After hearing the gunfire, he rushed into the street, where he met Nelson, who shot a single, fatal bullet into his chest as he fled. Witnesses are said to have heard the men laughing and firing a celebratory shot as they moved towards a waiting car.
Five weeks later, Nelson was charged with the murders, but the case was dropped due to insufficient evidence. It remained unsolved for eight years until new DNA technology enabled the police to obtain a full profile of Nelson from the blood and saliva he left on Danso’s clothing. They matched his DNA to the national database and arrested him in 2001 while he was already serving life for another murder he committed in 1996.
Nelson denied any involvement in the Cato Road murders and claimed he was framed. He refused to attend his trial and was convicted in absentia in 2006. The judge sentenced Nelson to life in prison with a minimum of 35 years and described him as a “psychopathic killer”, and one of the most dangerous men in the country.
5. The Cromwell Street Murders
The investigation into the Cromwell Street Murders (committed between 1967 and 1987) involved hundreds of officers, forensic experts, archaeologists, and psychologists. The operation began in February 1994, when police searched the Wests’ home at 25 Cromwell Street and discovered the remains of nine victims buried under the cellar, garden, and patio.
Fred West confessed to killing at least 12 women and girls, including his first wife and one of his daughters, and was charged with 12 counts of murder – while Rose West denied any involvement but was charged with 10 counts of murder. DNA evidence played a crucial role in identifying the victims and linking them to the couple.
The police used mitochondrial DNA analysis, which traces the maternal lineage of a person, to compare the bones found at Cromwell Street with the blood samples of the victims’ relatives. This method helped to confirm the identities of nine victims, including Heather West, Shirley Robinson, Alison Chambers, Lynda Gough, Carol Cooper, Lucy Partington, Therese Siegenthaler, Shirley Hubbard, and Juanita Mott.
The other three victims – Rena Costello, Charmaine West and Anne McFall – were identified by other means, such as dental records and clothing.
DNA evidence also helped to establish the time and cause of death of some of the victims, as well as the involvement of Rose West in the murders. For example, it showed that Shirley Robinson was eight months pregnant when she was killed and had been carrying Fred West’s child, suggesting a possible motive for her murder.
Other tests revealed that Heather West had been dismembered after suffering a fractured jaw and skull, indicating a violent assault. Plus, Rose West’s fingerprints were found on the tape used to gag and bind some of the victims, implicating her in the torture and murder of the young women.
Rose West was convicted of 10 murders in November 1995 and sentenced to life imprisonment without parole. She’s currently serving her sentence at HMP New Hall in West Yorkshire. Fred West hanged himself in prison in January 1995, before his trial could begin.
DNA evidence has revolutionised the field of forensic science and enabled the resolution of many chilling cold cases that had remained unsolved for decades. By using advanced techniques such as DNA profiling, familial DNA testing, and genetic genealogy, investigators have been able to identify suspects, confirm their involvement, and bring them to justice.
However, DNA evidence also poses some challenges and limitations – such as contamination, degradation, interpretation, ethics, and legal issues – and should therefore be used with caution and alongside other types of evidence to make sure results are reliable and accurate.
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