(Undated)  --  The case of the mysterious hijacker D.B. Cooper may be taking a new turn.  A crew of volunteer cold-case investigators in the Pacific Northwest say it's uncovered "potential evidence" in the 46-year-old mystery disappearance.  The group leader tells Fox News they found what "appears to be a decades-old parachute strap."  The D.B. Cooper mystery has confounded law enforcement and amateur sleuths for decades.  In 1971, a man calling himself Dan Cooper hijacked a jetliner, demanded 200-thousand in cash and then parachuted out of the plane.