Camera can reveal painted-over blood spots

Spattered blood intentionally painted over can be detected with a standard digital camera tweaked to record infrared light, Australian researchers say. The technology could become an important tool for cold-case investigators examining an old crime scene, they said. Glenn Porter, an expert in forensic photography at the University of Western Sydney in Australia, said he had heard of cases where investigators suspected that a crime had taken place in a now-remodeled house. With his colleagues, he decided to see if infrared photography might reveal blood hidden under paint, since the longer wavelengths of infrared are better at penetrating layers of paint. Blood that was completely invisible to a standard digital camera under two coats of paint could be seen in infrared even under six layers, Porter and his colleagues report in the Journal of Forensic Sciences. "We hope it gives law enforcement the ability to go on hunches," Porter told ScienceNews.org. "You can have your suspicions and then get a hit behind the paint," he said. "Then you decide if you want to start scraping paint off or take out a wall."