Tracing the DNA
Hidden in the courtyard of the Institute of Forensic Medicine stands a weeping beech, five metres high. It isn’t clear whether the tree – known in German as a “weeping blood beech” – is a clue to what lies behind the dark red bricks of the building in Röntgenstraße 23; but what is certainly clear is that anyone working in forensic medicine needs strong nerves.
Past the Department of Forensic Medicine, where for example autopsies, post-mortems and examinations of victims of violence or accidents are carried out, lie the forensic toxicology laboratories. Using pharmaceutical, chemical and toxicological methods, the experts here investigate unnatural deaths, poisonings and substance abuse. The third department contains the laboratories of the forensic molecular biology department. This team of biologists and biochemists carries out parentage testing, for example paternity tests, and analyses forensic evidence from crime scenes – also known as DNA traces – for judicial and law enforcement authorities.
“Trace material can include a wide range of things,” says Prof. Marielle Vennemann, who has been head of the forensic genetics laboratory since 2013. “It can be large traces such as clothes with blood on them, or instruments used for a crime, such as knives, or even very small traces such as single hairs or tiny skin flakes. We have even examined half-eaten biscuits and the remains of a piece of cream cake,” she adds.
The labs in the Institute of Forensic Medicine are bright and plainly furnished and are located very close not only to the Dermatological Clinic at Münster University Hospital, but also to University research buildings such as the Center for Soft Nanoscience and the Multiscale Imaging Centre currently under construction. After the Second World War the building complex was used by the British Forces as a military hospital. Until 1992, the Obstetrics and Gynaecology Department was where the Forensic Medicine Department is now.
Only a few people are admitted to the dissecting room and laboratories, as confidential files belonging to the Public Prosecutor’s Office and the police cannot be allowed to fall into unauthorized hands. Objects of investigation such as swabbing traces of burglary, gloves or face masks used in robberies are also kept in the exhibits storeroom at the Institute of Forensic Medicine. Just like a corpse, such objects contain many traces which can lead to the perpetrator of the crime. The top priority is cleanliness, because even the slightest contamination can falsify the lab results and have far-reaching consequences – for the perpetrator as well as for the victim.
The forensic laboratory is equipped with all kinds of technical machines and devices which are used in a certain sequence when a new work assignment comes in. “An average of 1,700 cases land on our desks here every year – and everything is strictly anonymous,” as medical laboratory assistant Ursula Sibbing explains. “But in fact we have far more traces from crime scenes to examine – around 5,000 a year – because, of course, one case can include several exhibits,” she adds. In their work, the team members don’t just work blind on their assignments: they regularly consult the police in order to learn more about the details and the context of a case and in order to then make the best possible assessment of the lab results.
The results are used for a comparison of DNA profiles between traces and individuals, for example suspects.“
But first things first: an exhibit first undergoes various preliminary tests in the trace lab. These tests include macroscopic and microscopic examinations of bodily fluids such as blood, saliva, urine and sperm. The traces identified then go to the extraction lab – a special “clean lab” – to isolate the DNA from the body cells. After this, the experts undertake a PCR approach (polymerase chain reaction), which is a genetic method of amplifying DNA samples. “With the aid of so-called capillary electrophoresis we can visualize the PCR products,” Marielle Vennemann explains. “The results are used for a comparison of DNA profiles between traces and individuals, for example suspects. If there is a match, it can be assumed with a high degree of probability that the trace comes from this person.”
In Germany, it was primarily the former head of the Institute of Forensic Medicine, Prof. Bernd Brinkmann, who established DNA analyses – and these are now being continued by the Director of the Institute, Prof. Heidi Pfeiffer. It was Bernd Brinkmann, incidentally, who was the inspiration for the character of forensic scientist Prof. Karl-Friedrich Boerne in a popular crime series on German television. Students of medicine and law were also taught under Brinkmann’s supervision.
Today, too, there are seminar rooms between the labs, in which students attend lectures and seminars on subjects such as child abuse, gunshot wounds and death by natural causes – as well as drug analyses and forensic DNA analyses. Being present at autopsies is also part of the curriculum.
The lab team is particularly proud of the opportunities which forensic medicine at a university presents – in research. “We have a lot of freedom to try out new methods and regularly exchange ideas with other scientists. A lot of PhD students also use the labs for research work,” says Marielle Vennemann. She relates how the team developed a method for analysing whether blood is a “normal” blood trace or menstruation – a very important method for most sexual offences such as rape.
Despite what are often dramatic cases, Marielle Vennemann and her team are passionate about their work, which they greatly enjoy. “Every day, the activities here are fascinating,” she says. “An awareness of the special responsibility that we have towards both the victims and the suspects is something that has really created a bond between us team members.”
Author: Kathrin Kottke
This article was first published in the University newspaper wissen|leben No. 4, 16 June2021.
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