Thank you, I really appreciate that. The documentary didn't portray Peter as he actually is. I agree he didn't come over well. He was hoodwinked to give a story of 80s misogyny which when edited didn't look great on him - times were very different then.
Statistically (80 ish percent depending on geographical location) it is someone known and usuallya partner. Peter Heron has an alibi from 2pm to 6pm with witnesses that include an off duty police officer, and people Peter actually spoke to. The case is however, littered with poor decisions on all parts from 1990 - 2005 to now.
The only evidence the police had against Peter was the DNA on his wife in his home ( nothing exceptional there) and the fact he initially lied about his journey route home. In the initial lie he would implicate him more. When his actual route was given it does give him a coverdd alibi, so the initial lie didn't benefit him - just a stupid thing to do.
There are recent developments which will be published in the media in the next week or so. Once they are public, I'll be able to elaborate more.
Regarding Benson, yes I believe he is a viable suspect. This is simplified but based on antecedents, efit, witness statements, psychiatric reports, and interviews with those who knew him, location and reason to be near, the car, his description, the confession. Hope that helps.