Detection of blood and DNA traces after thermal exposure.

The analysis of blood traces is often of significant reconstructive and evidence-gathering importance. Perpetrators deliberately set fires to destroy evidence. There is little literature regarding the effect of fire and extreme heat on blood and the detection of blood. Blood and DNA are believed to be no longer traceable after exposure to a temperature of 1000 °C. This study exposed different objects of a standardized procedure to temperatures of 300, 700, and 1000 °C. It documented the influence of heat on blood traces through the use of luminol. DNA analysis confirmed that fewer DNA profiles can be created with increasing temperature. However, even after exposure up to a max. of 1000 °C, it was still possible to produce a complete DNA pattern from approx. 60% of the samples. Consequently, crime scenes that have been destroyed by fire should be evaluated with the same attention to detail as the unburned areas.