>> he paged me, saying, "you know what, i need a ride." >> reporter: the prosecutor argued that if they were together and javier's dna put him at scene of the crime, then sam had to be there too. his alibi is at theurder scene. and for sam lopez, i think that's just devastating evidence. >> reporter: and he told the jury it was the first of many instances where the most powerful evidence of guilt came from sam's own words. >> it's sam's actions and it's sam's statements. >> reporter: so he gave you the case against him. >> the best evidence that we have in this case, and that we had, was sam lopez himself. >> reporter: sam was the one who told police he had a jealous streak. >> every time she mentions some guy's name, i get pissed off, okay? >> reporter: cathy was seeing another guy -- albert. the prosecution said sam's jealousy was triggered the night he took cathy out and saw that hickey. >> what effect is that going to