The technology could enable cold-case investigators to better examine old crime scenes, 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 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."