detective mehl chased down a 2001 walmart receipt, a minor, forgettable purchase, except that the timemp on the receipt cast doubt on philip barr's alibi didn't exactly wreck it, but it caught him in a significant lie. >> that's how detailed we were getting. >> reporter: and then they just happened to run into a guy who said he knew barr and mcmannis and peewee. >> and he overheard them talking about killing this girl. he heard david mcmannis say, "we shouldn't have done that girl that way. if i don't get out of town, i'm gonna spend the rest of my life in jail." phillip barr said something similar because peewee is talking about, "well, i've only seen a body. it's not against the law to see -- see a body." and barr tells him, "hey, shut up. we're all gonna end up in prison." >> and it was somebody with credibility. >> better than what we had before, yeah. >> reporter: but overall, a key problem remained. >> terrible witnesses. >> reporter: meaning detectives spoke with other people who'd also heard the men talk about the murder, but they were not the type a jury would likely believe.

detective mehl chased down a 2001 walmart receipt, a minor, forgettable purchase, except that the time't exactly wreck it, but it caught him in a significant lie. >> that's how detailed we were getting. >> reporter: and then they just happened to run into a guy who said he knew barr and mcmannis and peewee. >> and he overheard them talking about killing this girl. he heard david mcmannis say, "we shouldn't have done that girl that way. if i don't get out of town, i'm going to spend the rest of my life in jail." phillip barr said something similar because peewee is talking about, "well, i've only seen a body. it's not against the law to see -- see a body." and barr tells him, "hey, shut up. we're all going to end up in prison." >> and it was somebody with credibility. >> better than what we had before, yeah. >> reporter: but overall, a key problem remained. >> terrible witnesses. >> reporter: detectives spoke with other people who'd also heard the men talk about the murder, but they were not the type a jury would likely believe. much of what they'd say sounded like drug and booze soaked