The quantitative alteration of the DNA content in strangulation marks is an artefact

It is frequently difficult to prove the vitality in cases of fatal hanging. Using impulse cytophotometry, Müller et al. (Krim. Forens. Wiss. 44, 1981) reported on possibly vital alterations of the DNA content in five strangulation marks (hypodiploidy). The objective of the present study was to perform a re-evaluation by means of current methods of quantitative DNA analysis. The investigation included 24 cases of hanging (typical, n = 11; atypical, n = 13). DNA was extracted by use of phenol/chloroform and quantitated photometrically in relation to the tissue weight. In addition, skin specimens were examined histologically and their water content was determined. The mean DNA content of strangulation marks was 3.2 micrograms DNA/mg tissue, that one of uninjured skin (control) 1.4 microgram DNA/mg tissue. The ratio of DNA content between strangulation grooves and control skin varied from 1.2 to 5.2 (average: 2.4) implicating apparently elevated DNA levels in strangulation marks. Histology revealed typical changes with absence of leukocyte infiltration suggesting mechanical compression of DNA containing layers. The additional determination of the water content emerged-in dependence on the macroscopic appearance, dried or non-dried-reduced values for strangulation marks (average: 42% vs. 66%). Statistical analysis demonstrated a significant correlation between elevated DNA content and reduced water content of strangulation marks.

the markedly elevated DNA content of strangulation marks is interpreted as an artefact due to drying of the skin with a reduction of the water content (and weight) in the course of mechanical cutaneous alterations (compression). Therefore, quantitative changes in the local DNA content of the groove have no importance as a sign of vitality in fatal strangulations.