Detective Lt. Nicholas A. Paonessa is using a high-tech forensic tool called the Rofin Polilight PL500 to prove that a farm in Pennsylvania was used as a field hospital after the Battle of Gettysburg in 1863.
Records show that farmer Daniel Lady and his family returned to a home filled with wounded soldiers and bodies.
Paonessa's investigation is confirming that story. In the darkened parlor, on his second trip to the farm since September, Paonessa pointed the bright blue light at a vaguely human outline on the wood floor. The shape became a distinct form, from head to knees, of a small-framed man. Four spots by a baseboard were revealed as being the fingerprints of a person sitting against the wall.
Theoretically, Paonessa said, old blood could reveal the victim's identity. Identification would require a well-preserved blood sample -- from between floorboards, for instance -- and a known descendant for comparison. [Link]