reporter: but he also knew he was working with a cop on a mission. daron wyatt was not gonna quit until i filed this case or i died. or he died, i guess. daron was absolutely dedicated to this. reporter: the truth was if murphy declined the case a third time the cathy torrez file would almost certainly go from cold to dead. what would he decide? no one understood the stakes better than cathy s mom. daron had told meal that we were going to meet with the d.a. my interpretation of it was that he was going to tell me that there was nothing they could do. coming up a key piece of evidence arrives. better late than never. how long had they known that? a couple of months at least. and they what, forgot to call? is it the smoking gun? when dateline continues. you okay? eczema. it s fine.
eight to bring him to trial. and just months before that trial began, matt murphy learned that sam had a new defense attorney. someone matt knew very well. he is so good, and would be lyin if i said my heart was not in my throat. reporter: sam s defense attorney lew rosenblum was the former assistant da who supervised the homicide unit. in fact, he was the original prosecutor, who back in 1994 didn t think there was enough evidence to charge sam. not only that, lew was the man who brought matt into the homicide unit. lew took me under his wing and trained me how to do homicides. what s it like to go up against your mentor? well, it s terrifying to go up against your mentor. reporter: neither one of them had ever lost a murder case. but someone s winning streak was about to end. february 10th, 2015. 20 years after cathy torrez murder, sam lopez went on trial.
alone. just as prosecutors now believed he wasn t alone the night he stabbed cathy to death. sam s cousin xavier was also arrested and charged with murder. police also arrested sam s older brother, armando, who was once married to cathy s sister tina and had helped search for cathy. it s just a tragic loss. it hurts. everybody loved cathy. reporter: armando was charged with being an accessory after the fact for allegedly helping cover up the murder. we believe that he was telling people who had information that could help convict sam not to cooperate with the police. reporter: cathy s sister had to ponder what that might mean about her former husband. betrayal of the worst kind. betrayal of her, betrayal of you. exactly, everything. your family. my family. trust, betrayal, everything s broken beyond belief. reporter: sam and his wife had also separated by this
happiness is powerful flea and tick protection from nexgard. nexgard kills fleas and ticks all month long. and it comes in an easy-to-give tasty chew. and that makes dogs and owners happy. no wonder vets love it too. reported side effects include vomiting, itching, diarrhea, lethargy andack of appete. see your vet for more information on flea and tick protection you and your dog will love. nexgard. the vet s #1 choice. reporter: prosecutor matt murphy thought daron wyatt s investigation of cathy torrez murder was compelling. but he knew that making the case against sam lopez wouldn t be easy. the d.a. s office had declined to try it twice before. so murphy called for help from a detective whose legendary skill with cold cases has earned him a
tried to contact him after she disappeared. i thought she was gonna page me on friday. she goes somewhere, and she never paged me on friday. we know that cathy s mom paged him 20 or 25 times in a matter of at least a couple of days, trying to get him to contact her because he s so close to cathy and she s missing. reporter: montgomery noted a key detail about those pages. mary s home phone and cathy s home phone arehe same mber. they re the same numbers. reporter: so, seeing that number on his pager. how did sam know it wasn t cathy? if he knew she was alive, he would know he got 20 or 25 pages from cathy, or at least think that. if he s guilty and he killed cathy, he knows those 20 or 25 pages were not from cathy. reporter: that was tell number two. then montgomery noticed how, in his second interview, sam referred to cathy s murder. you know? but then happened, and shoot. he doesn t use the word murder, doesn t use doesn t