[Differentation and timeinterval for detection of tissue cells on a weapon used in a crime (author's transl)]

There are numerous methods of examining the weapon used in a crime to detect evidence of blood or of blood-group properties. Forensic literature also contains references to the tracing of organic tissue. In the case against Jaccoud the two medical experts called upon, UNDRITZ and HEGG, found evidence of cells from internal organs on a knife which had possibly been used to commit the crime and which had been stored away for some considerable time. Practical experience has shown that the likelihood of finding cells on the weapon used is small; however, it is greater in the case of abdominal injuries than in the case of stab wounds in the chest. Tests carried out on corpses have revealed evidence that cells from the liver can adhere to a blade plunged into the organ. This happens mostly when a knife with a serrated or wavy edge is used. The abdominal wall has a greater cleaning effect on a blade than clothing does. It is of crucial importance to clarify the environmental conditions to which an object bearing certain traces has been exposed. Over a long period of time it is much easier to detect parts of organs if they have been subjected to swift dehydration (by the wind, for example). A location which is either warm or damp and humid makes identification, even after a few hours, no longer possible. The presence of a single tissue cell, especially if it should have managed to retain its structure after several months' dessication, can never suffice for an organic diagnosis. How many determining characteristics then must be traceable? And how great is the certainty of identification with regard to cells from other organs or to nun-human cell structures - all of which are also subject to environmental and time factors? How many single tissue cells must be identified to determine conclusively that the cells in question came, for example from the liver?