This story took place in London in the 1990s. It was told in 2014 in an interview with the BBC by forensic scientist Michael Silverman. The press dubbed the case "The Strange Time Killer Case."
In the late 1990s, a woman was brutally murdered in London, and during the investigation, tiny pieces of cells were found under her nails, which, when tested for DNA, indicated … another murdered woman, whose body was found three weeks earlier.
How is this possible? This mystery baffled detectives and doctors. Maybe the analyzes were wrong? Maybe these particles were old and accidentally got on her body? But no, everything was correct and everything indicated that the murdered woman had scratched her killer shortly before her death.
The two murders took place in different parts of London and the victims did not know each other. Then the question arose that something unusual had happened.
Then it was checked whether the materials were not confused when they entered the laboratory, but this also turned out to be without errors, nail samples from these two women were received on different days and were not even nearby.
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Forensic autopsies are usually performed on the bodies of people who have died a violent death or their death looked very suspicious. These autopsies are much more thorough and complex. than usual. Samples of fluids, tissues, organs are collected for a toxicology laboratory, stomach contents are taken, nails are trimmed and scraped off.
According to Silverman, he started working as a forensic scientist back in the 1970s, and then the very idea that tiny droplets of blood or pieces of skin and nail cells could indicate a killer seemed to all science fiction.
Further research by Silverman showed that contamination in the form of DNA from the opened bodies is also found on other tools of the morgue, even well-washed ones. However, since nail samples are taken only with scissors, they were the first to be caught with the evidence. After careful examination of these scissors, traces of the DNA of many previously opened bodies were found on them.
After that, Silverman notified all the morgues in the country, and also announced his discovery to investigators and coroners. From that day on, all nail samples taken were to be carried out with disposable scissors and the same disposable scissors with which the samples were taken should be attached. This system continues to operate in the UK to this day.
Modern DNA analysis is so sensitive that foreign DNA contamination is a big problem and can lead the investigation down the wrong path.
In 2007, DNA traces of a girl were found at the scene of a murder in Germany, which, when searched in a DNA database, showed five murders in France, Germany, as well as several thefts and thefts.
This girl was involved in at least 40 different crimes!
For two years, the authorities searched for this woman, who seemed to them to be a cruel serial maniac, but in the end it was found that all these traces belong to a woman who worked in a factory for the production of test bottles. The woman accidentally touched the jars with her unprotected hands and left traces of her DNA on them. When materials from crime scenes were put into these jars, the DNA of this woman also fell on them.