Winward1 if Thoreson had committed previous crimes and caught don't you think there would be fingerprints on file? Why not compare with the thumbprint and partial found at Percy home. Why all the sudden it is a bayonet knife when the bashing in the head Valerie took left diamond shape marks, if I am not mistaken. They never could explain that and what kind of tool. Plus, carrying all the tools to break in and kill Valerie. I honestly have a hard time with this one. I am not done reading the book and might change my mind when I do finish it, but I would think the PD would have done their homework more thoroughly now or back then.
Some of these things, like why the impressions on the victim's head were as they were reported, indicate the pummel of that particular bayonet. Remember, most of the reporting on the head wounds came prior to the discoverey of the bayonet. Murder was on a Sunday. Bayonet was found Wednesday afternoon. Things were said prior to the discovery about fireplace pokers and sharpened metal objects. But that was before they found it, and it was a very uncommon weapon to be used in the murder of a civilian in a suburb that had never had a murder, despite being one of the oldest in the area.
Far's the prints go, there are a number of open prints in this case. There's no indication that any of them were the offender's save the bloody palm print, which may have been useless. There is evidence he was wearing gloves. If it was Thoresen, his wife said he said, with not a little credibility, that he murdered, and or had murdered at his direction, three others and was never charged in those crimes. Remember, she was acquitted for shooting him five times in the back in a jury trial. That was no small feat in 1970, when spousal abuse was not a known term. He was one diabolical dude.
As for sets of prints, it's clear that they didn't have a full set. The FBI documents reveal one of the reasons they wanted to talk with Thoresen is because they wanted to obtain a full set of prints. Yes, he had an extensive criminal history on the North Shore. But it was not a place, ahem, well known for top police work.
That stuff is all in the book, which has a lot of info about Thoresen. Plus there is Thoresen's wife's book. I'm not trying to do either of them justice here, because there's a lot more info in them. At least you have one of them so you can decide for yourself.