The body of a woman was found in London, England. The DNA test results left the police baffled, as the suspect appeared to have died weeks before the victim. This is one of the strangest cases that British forensic expert Dr. Mike Silverman has ever witnessed in his career.
The Mystery of the Suspect Who Died Weeks Before the Victim
According to Dr. Silverman, this case was a real-life mystery: a woman brutally murdered in the capital, London. Biological material found under the victim’s nails suggested that she might have scratched her attacker just before dying. A sample of evidence was sent for analysis and quickly matched with entries in the UK national DNA database.
What was shocking was that the evidence identified a woman who had been murdered three weeks before the death of the aforementioned victim. The two murders occurred in different areas of London and were investigated by separate teams.
As there was no apparent connection between the two women, nor any indication that they had ever met, authorities concluded that the evidence samples had likely been mixed or contaminated at a specific point—possibly in the forensic laboratory. A senior official involved in the investigation officially lodged a complaint.
The incident occurred in 1997. At that time, Dr. Silverman was the head of the UK Forensic Agency, tasked with investigating whether any errors occurred in the forensic laboratory.
Initially, Silverman speculated that perhaps the nail sample from the second victim had been mislabeled and actually belonged to the first victim. However, upon examining the sample, he found this assumption to be incorrect.
Dr. Silverman then meticulously reviewed all records from the forensic laboratory to see if the samples were inadvertently mixed in some way. Ultimately, he discovered that both bodies underwent autopsies at the same morgue, even though they were brought in weeks apart and processed by different forensic teams.
Unraveling the Confusion
Forensic autopsies, which are performed in cases of murder or suspicious deaths, are carried out with much more thoroughness and care than regular autopsies. In these cases, specialists collect blood and organ samples for toxicology tests, analyze contents from the stomach, and separate and cut the nails of the deceased.
While reviewing the morgue’s records, Silverman suddenly found the key to unlocking the mystery of the case. It turned out that the first victim’s body had been kept in refrigeration for weeks while the police conducted their initial investigation. The body was removed from the freezer so that pathology experts could take additional nail samples before the second victim’s body was transferred to the morgue.
The following day, the same nail clippers were used to cut the nail samples from the second victim. Although the clippers were sanitized between uses, due to an oversight, genetic material from the first victim remained “contaminated” and transferred to the nails of the second victim, leading to the bizarre DNA analysis results.
Results from the analysis of the forensic nail clippers even revealed that not just two, but three distinct DNA samples existed on them. DNA contamination was also found on several other tools in the morgue, such as autopsy knives, but did not pose a problem as they were not used to extract DNA samples.
Silverman immediately sent an urgent memo to all investigators, forensic experts, and morgue staff across England, outlining the issue and requesting that in the future, all nail cutting should be performed with single-use clippers, which would then be placed in a evidence bag along with the nail samples to verify this. This procedure is still followed to this day.
Challenges of Modern Times
Modern DNA analysis is so sensitive that contamination has become a significant issue, as it can lead investigations astray. In 2007, in Germany, DNA traces belonging to an unidentified woman were found at the scene of a police officer’s murder. When compared to the German database, the identical DNA appeared at the scenes of five other murders in Germany and France, as well as at numerous theft and car theft sites. In total, the woman’s DNA was recorded at the scenes of 40 separate cases.
German authorities spent two years searching for the perpetrator, only to discover that the DNA in question actually appeared on swabs used by investigators to collect samples at the scene. These swabs had inadvertently been contaminated by a woman working for the manufacturing company.
Over the years, DNA has been seen as the ultimate weapon against crime, successfully exposing the perpetrators of cases with less evidence. However, Silverman notes that in many ways, DNA analysis can become a victim of its own success if the processes of collection, handling, and analysis are not conducted carefully to eliminate the possibility of confusion or contamination, or a lack of corroborating evidence linking it directly to the case.
