why didn't you say something at the time to someone? >> reporter: he is certain elizabeth ratliff died of a stroke. as for how his wife, kathleen, died years later, michael can't say for sure. but he thinks his first instinct was the right one. >> i guess maybe i'm the last person to believe it. i think she fell down the stairs. i don't know. >> reporter: michael believes alcohol must have played a role in her fall, and even though her blood alcohol levels weren't off the charts, he says, there may have been another contributing factor. a few months before her death, she'd suffered an injury diving into their swimming pool. and her doctor put her on several prescription meds. >> do you remember her being wobbly in the weeks that followed? >> oh, my god, yeah. she had to wear a neck brace. she -- they put her on percocet to begin with. then they brought valium. she was on flexeril which is, apparently, a muscle relaxant -- oh yeah. she was in a great deal of pain all the time. >> reporter: for michael peterson, the trial was hard enough to bear, but the family spilt made it even worse. there was kathleen's daughter,