Microbe Detectives: New Clues to Old Crime Scenes

Determining how long a stain has been on a surface can be crucial in solving crimes, but it's not always easy. Scientists have looked into DNA and RNA markers, but these require high-quality samples. Now, they're turning to tiny organisms called microorganisms, which can act as unique markers to help guess the age of blood and semen stains. Blood and semen are common finds at crime scenes, yet we don't know much about using microorganisms to figure out how old these stains are. This study looked at stains kept indoors for up to 56 days, focusing on specific microorganisms that live in blood and semen. These were picked using a method called 16S rRNA high-throughput sequencing.To check if these microorganisms worked well, the scientists used another method called qPCR on separate samples kept in the same conditions. They also built two special models to predict how long the stains had been there. The results were promising: for three types of body fluids, the average difference between predicted and actual ages was around 2 days. This study found four new microorganisms related to the age of blood and semen stains and created initial models to predict their age. This could be a big help for forensic science in the future.