And of course he can't prove that because he would say "the man paid cash".
The police said his wife wasn't under investigation, but I just can't believe she wasn't very suspicious that he'd committed the murders. She had already commented to him that the car and trailer looked like his. Did she not think it strange that he sold the trailer? Trailers must have number plates, so what lame excuse did he have for selling it without one? Add to that she photographed him painting his car - the third time in 7 years.