The Achilles tendon as a DNA source for STR typing of highly decayed corpses

Forensic criminal casework often involves DNA profiling of human postmortem tissues, whereas degradational processes can affect PCR-based Short Tandem Repeat (STR) analysis. Degradation of DNA is observed to vary among different tissues and with time. Therefore, the stability of DNA in Achilles tendon samples is compared to that in muscle and kidney specimens with a variety of postmortem histories. Tissue samples from 28 autopsy cases, including 15 decomposed corpses and a control group of 13 nondecayed corpses were analysed. DNA was isolated using the All-tissue DNA Kit (GEN-IAL, Troisdorf, Germany), quantified by spectrophotometric measurement, amplified by the multiplex PCR genRES MPX-2 (Serac, Bad Homburg, Germany), and analysed on the ABI PRISM 310 Genetic Analyzer (Applied Biosystems, Darmstadt, Germany). Quantitative analysis of nondecomposed tissues revealed that the recovery of DNA was highest in kidney followed by muscle, whereas Achilles tendon tissue was the poorest source of isolated DNA. Only small amounts of DNA were present in both kidney and muscle samples from decomposed corpses. However, from decayed Achilles tendon samples twice as much DNA as from nondecayed samples could be isolated on average. These results suggest DNA to be better protected in Achilles tendons. Moreover, postmortem changes in Achilles tendons may even improve DNA isolation.