Of all the daft ideas I've heard lately, the call to re-open the Crewe murder case would have to be one of them.
For starters, the killings happened 40 years ago. A man went to prison for the killings but was later pardoned after the police were caught planting evidence.
And there's also the tricky problem that many in the police still think Thomas did it. Having read quite a bit about the case over the years I've never felt there was sufficient evidence for Thomas' conviction, but try telling that to the cops. I've spoken to a few police officers over the years about the case, and most who have an opinion on the case maintain he did it. I guess it's hard to accept that two of your own would disgrace the force by planting evidence. The cops will tell you "if only you knew what we know," as if they are the keepers of some hideous secret that cannot be released, even though it's almost certain they have nothing on the man that hasn't already been made public.
So what are we going to find out forty years later? I suppose it's possible there may be some DNA lurking somewhere in an evidence box that could be tested (although much of the evidence will have been destroyed), but even if DNA could be obtained, what good would it do? Who would you match it to? There's a strong possibility that any DNA police found would belong to someone now dead. That would make any matching of DNA a challenge.
And, in the end, what's to be achieved by reopening the enquiry? Everyone has a theory on who did it, but most people who don't think Thomas did it think it was a murder-suicide (nobody agrees on which Crewe fired the bullets), and many are convinced that Jeanette Crewe's father Len Demler was somehow involved (either as the murderer, or as the person who cleaned up the mess). Those theories are certainly more plausible than the original police theory of the case.
The Crewes are of course dead, and Demler died in 1992. No genuine suspect has ever been identified, other than Thomas. Absent a confession or a startling new piece of evidence, reopening the case would seem to be a waste of police resources.