NBC News 
April 20, 2013
Thermal-imaging devices have been used to seek out pot-growing operations, map Martian geology — and now, to watch the second suspect in this week’s Boston Marathon bombings as he was holed up in his last hiding place.
Authorities said a helicopter equipped with a thermal imager spotted the heat signature of a person inside a tarp-covered boat, sitting in a backyard in Watertown, Mass. Police used the sensor after an area resident reported seeing a trail of blood leading to the boat — and catching a glimpse of a blood-covered body inside. The thermal readings confirmed that there was indeed someone under the tarp, and that the person was still alive.