As everyone else suggests, try the local newspaper archives. It's really weird there is a distinct lack of coverage of major crimes in the 1960's and 70's even in news archives though. When I was younger my mother pointed out a house in Worcester where a man who had been babysitting three young children decapitated them all and stuck their heads and bodies on the railings outside the house in the 70's. At the time I could find out absolutely nothing about it, then a few years ago he made an attempt to be released and the Daily Mail got hold of it but the local papers of the time hardly covered it at all, which I find completely bizarre given the nature of it.