I thought they did a decent job of explaining the DNA issue at least as matching goes. I think of it is a a funnel, where they had 16 Y-STR markers, which indicated 30M people (I'm making up the #s), then with 25 the funnel narrowed to 10M people, and the person mentioned was excluded. You ultimately narrow the funnel with additional markers, which leads to one person.
What I do not understand is the difference among samples - not a biologist but I thought on the DNA / cellular level saliva, semen, blood, skin cells, etc., carried full DNA profiles. Said more simply, in my ignorant mind if you had DNA you "had it all," i.e. a complete profile. I get technology has improved to be able to get better results from smaller samples, but the analysis being done with touch DNA is mind-blowing. Hoping for a surly biologist to explain it to me.
There was a cold case recently cracked in Fort Worth, where they were able to use a tiny amount of DNA on the victim's bra and dress to find a match.
It is crazy that in 30 years no one has ever confessed to someone while drunk, stoned, etc., or could just keep it in without telling someone.