Detection of blood and DNA traces after thermal exposure

Abstract

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.

Study on the methods of visualizing bloodstains after thermal exposure

“…Conventionally, detecting bloodstains at fire scenes has been regarded as a complicated challenge. However, the belief that high temperatures or fire can utterly eliminate traces and evidences has been decisively overturned [1][2][3][4]. Therefore, detecting bloodstains at fire scenes received increased attention.…”

“…Chemical reagents [2][3][4][5][6][7][8][9][10] and infrared photography [10][11][12][13] are both commonly used for visualization enhancement.…”

“…However, following a duration of 3 min under the temperatures ranging from 400 to 600°C, the fluorescence emitted from the heated bloodstain notably diminished when spraying any of these three reagents. Klein A et al [3] used torches to control temperatures at 300, 700, and 1000°C. The researchers sprayed luminol onto common tools, including copper pipes, cast iron pipes, tiles, axes, screwdrivers, and knives, which were stained with blood.…”

“…However, after comparing their experimental results, disparities have surfaced, primarily due to the disparate experimental methods, especially the diverse heat sources used for bloodstain heating. These heat sources ranged from torches, homemade heating furnaces, and alcohol lamps in smallscale simulations [2,3,5] to full-scale flashover environments in building fires [4,6,13]. The lack of strict control over heating temperature, duration, and their combinations in these studies is likely to result in varying outcomes [3,4,7].…”

“…These heat sources ranged from torches, homemade heating furnaces, and alcohol lamps in smallscale simulations [2,3,5] to full-scale flashover environments in building fires [4,6,13]. The lack of strict control over heating temperature, duration, and their combinations in these studies is likely to result in varying outcomes [3,4,7]. In addition, a systematic comparative analysis on the effects of two visualization techniques, chemical enhancement reagents and photography, on visualizing bloodstains exposed to the same thermal conditions remains unexplored.…”