Detection of painted-over traces of blood and seminal fluid

Dealing with a refurbished crime scene is a special challenge for forensic investigators. In such cases, a crime scene may not have only been cleaned in order to erase all traces but the walls of an indoor crime scene could also be painted over in order to mask traces of the crime. So far, very few publications have shown that painted-over traces of blood and seminal fluid can be detected using a forensic light source or infrared photography. To date, there have been no systematically executed research studies including guidelines on which settings to use depending on the color of the wall. Moreover, no comparative study has addressed the question of whether it is better to use infrared photography or a forensic light source to visualize painted-over bloodstains. The present study covers the aforementioned gaps and shows that painted-over bloodstains are most easily visualized by infrared photography, while traces of seminal fluid are most easily visualized at 440 nm in combination with a yellow filter-both independent of the color of the wall paint.