according to greer, that means adam, who had no criminal history, knew exactly how to wipe down the scene, somehow removing his own fingerprints and dna, but leaving just rebecca's. of course, it could also mean that adam simply wasn't there when rebecca died, which is exactly what law enforcement came to believe. i'm guessing that if you walked in at court on any case and opposing counsel said, "there is no evidence here, and there is no fingerprints, and there is no dna, and that is the proof of the case that i am bringing," you would think to yourself, "i got a groundball here." >> the absence of evidence isn't the evidence of absence. and so we know it's murder 'cause it's wiped down. we know it's not suicide. >> reporter: would a jury agree? greer had to prove adam shacknai was somehow responsible for rebecca's death, that his own actions made him liable.