definitively serrano s, but very much like one he once owned and experts examined. the wear pattern is consistent with the shoe that stepped on that vinyl chair in december of 1997? absolutely. reporter: prosecutors knew they would have to shred serrano s alibi that he was in atlanta for a business trip and not in florida for the lethal business of murder. people would go to atlanta, they would find him on the videotape, he would be alibied and nobody would ever look any further. and that would be the end of it. in terms of being diabolical, that s a pretty good alibi. reporter: they laid out their evidence for serrano being in florida that day. they called the nephew who rented a car for his uncle and he told a damaging story. the day after the murders, he said his uncle ordered him to retrieve that same car in the tampa airport parking garage and drop it off at the rental company.