The trial of William Barnes gets underway Monday. Barnes, now 74, is accused of killing Philadelphia Police Officer Walter Barclay. Barnes shot Barclay in 1966, but Barclay didn't die until more than four decades had passed. Barnes has already served 26 years in prison for attempted murder in the shooting. A host of expert witnesses are expected to take the stand, debating whether or not Barclay's death was caused by the gunshot wound that left him wheelchair bound for 41 years. Jim Strazella, a professor at Temple's Beasley School of Law, says it's a tough sell: "That will be totally one way or another by how clearly the evidence goes in. I'd want to see how that goes in before I'd even make an attempt at a guess at how it should come out."