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Proteins help to narrow down the time of death

Forensic scientists often have to determine the time of death of a person in both crime- and non-crime-related deaths. This is very difficult if the body is found a long time after death. The forensic scientist, Dr. Frank Wehner, from the University of Tübingen, has developed a method that enables him to determine the time of death to within a few days. The method is based on the degradation of proteins.

Dr. Frank Wehner (Photo: private)
When a body is found, forensic scientists are called to the scene to investigate the cause of death. However, in the case of unresolved deaths or murder victims, accurate information about the time of death is equally as important as its cause. Forensic scientists usually look for death spots which occur 30 minutes after death as a result of hypostasis, and for the onset of increasing muscle stiffness and rigor mortis which becomes obvious several hours after death. However, these signs are no longer visible a few days after death. If a person died long before he or she is actually discovered, entomologists, i.e. specialized insect researchers, can determine the time of death due to the fact that cadavers are colonized by certain insect maggots in a surprisingly fixed chronological order. Dr. Frank Wehner of the Institute of Legal Medicine at the University of Tübingen has developed another method that also enables a fairly accurate determination of death in cases where the death occurred longer ago. Wehner’s method is based on the degradation of body proteins.

Autologous proteins as witnesses

Frank Wehner found out that the new method worked with proteins that are present in many human beings. “One such protein is insulin, which only people suffering from diabetes type I are lacking,” said Wehner explaining that he wanted to use proteins that are present in sufficient amounts in organs that are routinely removed (e.g. pancreas or thyroid gland) in post mortem examinations. He also found it easier to use proteins for which antibody tests were available. Such tests are for example used in clinical pathology. The protein cystatin C seemed perfect; it is produced in the adrenal glands. The researcher has examined several hundred human cadavers of which the time of death was known in order to be able to better assess the affect of ambient temperature on degradation processes. Wehner also carried out experiments with mice that were killed after experimental procedures. Wehner left some of the mice outdoors and some indoors. “In mice, degradation progresses more rapidly than in humans because of their small body mass. But the results were nevertheless similar to those obtained with human cadavers,” said Wehner.

Cystatin C can be detected in an adrenal gland biopsy up until twelve days after death. A positive immune reaction tells the scientists whether cystatin C is present. “When we find a human cadaver in the forest and detect cystatin C, then we know for sure that death occurred no more than 12 days ago,” explains Frank Wehner. “If no cystatin is detected, then we know that death must have occurred at least three or more days ago.” The accuracy of the immunohistochemical assay used to determine the time of death can be improved by testing several proteins. Wehner and his colleagues know of seven proteins where the length of time they can be detected in cadavers is known, including glucagon, an antagonist of insulin in the blood sugar metabolism, and thyroid hormones.

“The time of death can be determined using immunohistochemical methods. When death has occurred a long time ago, then these methods enable the determination of the time of death to within two to three days,” said Wehner. This method is used in homicides, for example when a partially decayed cadaver with shot or stab wounds is found. The determination of the time of death is necessary for further investigations. In the majority of cases, murderers are neither clever enough to include methods such as protein detection in the planning of murders nor can they outwit forensic scientists. “Usually, murders are related to personal relationships with motives such as love, hate, lost love or money. Such acts happen without pre-meditation,” said Wehner.

Insulin provokes curiosity as a murder weapon

The reason why Wehner decided to use protein staining for determining the time of death is due to a case in which insulin was used as a murder weapon. Wehner wanted to provide evidence that a doctor had killed his parents. “Many people forget that physicians have access to tools and substances that can be used to kill,” said Wehner, adding that “Insulin intoxication is difficult to prove.” The corpses of the doctor’s parents revealed small puncture marks that appeared to be caused by syringes. The doctor claimed that he administered his parents morphine to ease their pain. However, no morphine was detected in the cadavers. Instead, the forensic scientists found a large amount of insulin, also around the puncture marks caused by the injections. The doctor was therefore judged guilty of homicide. This murder led to a debate among Wehner and his colleagues as to how long insulin could be detected in the body. “This clearly piqued our curiosity and the basic idea was born,” recalls Wehner.

As with any other method, the application of Wehner’s immunohistochemical method has its limits. “For example, cadavers that have been stored in freezers are unsuitable,” said Wehner who used glacier corpses that had been buried in ice for one to two years. “Refrigeration stops the degradation processes.” In a sauna, in contrast, the degradation processes progress a lot more rapidly than normal. That is why it would be impossible to determine the exact time of death in people found in hot environments. However, already established methods do not always provide the necessary evidence. For example, the insect method cannot always be used: “If there are no flies to lay eggs, then there won’t be any maggots. Some apartments are so clean that not a single maggot can be found. That’s not very common, but it happens.” The new method can thus nicely complement established methods when it comes to determining the death of older cadavers, adds Wehner.

“Quite recently, I was involved in an investigation in which the immunohistochemical method led to the required evidence,” said Wehner recalling that on 30th March, a man went to see his new landlord to pick up his key in order to move into his new flat. Just a few days later, on 7th April, the man was found dead and the cadaver was already degraded to a large extent. But the exact time of death was unknown. The deceased had a grandmother who died on 4th April, as well as a brother. “In terms of inheritance, the case was highly explosive, because the old woman had a beautiful villa, worth millions, to bequeath,” said Wehner. There were two possibilities: If the grandmother died before her grandson, then the inheritance would have to be divided in equal parts between the dead man and his brother. The brother of the dead man would not necessarily have inherited his brother’s share. It can also be assumed that the dead man’s children, for example, would have inherited the fortune. However, if the man died before his grandmother, then his brother would have been the only heir. “The new method showed that the man must have died no later than 1st April,” said Wehner. Therefore, the dead man’s brother was the sole heir of the fortune.

Source: University of Tübingen - 12.02.2008
Further information:
Dr. Frank Wehner
Institute of Legal Medicine
Nägelestraße 5
72074 Tübingen
Tel.: +49 (0) 70 71/2 97 20 67
Fax: +49 (0) 70 71/55 17 32
E-mail: frank.wehner@uni-tuebingen.de

Website address: https://www.gesundheitsindustrie-bw.de/en/article/news/proteins-help-to-narrow-down-the-time-of-death