I think that Justice Scotland gets this one right. It's admittedly difficult to defend yourself against a murder charge for something that happened 26 years ago. As a result, sometimes, we shouldn't allow such belated prosecutions.
But when the reason you're eventually charged is because you've been definitively linked, though newly available DNA evidence, to a brutal rape and murder, you're legitimately subject to prosecution. Yes, the crime occurred in 1976. Which is a long time ago, not only temporally (and culturally!), but also as regards the availability of witnesses, evidence, and the like.
Quite frankly, however, my instinctive reaction is that this is simply yet another good reason not to commit a murder. Or any other criminal offense with a long -- or infinite -- statute of limitations. Because, eventually, the police may catch up with you. Which, quite frankly, I hope they do. And when they do, we're not going to let you off merely because you've remained free during the past 26 years. By contrast, and just as a reminder, the victim has remained dead that whole time. So, honestly, even with the belated prosecution, you still got the far better end of the deal.
Yes, yes, I know: Maybe the defendant is actually innocent, and the delay in bringing him to court will allow an innocent man to be incarcerated. But my strong sense is that there wasn't much of a risk of that happening here; or, at a minimum, that the delay here didn't make it especially likely for Nelson to be convicted even if he was in fact innocent any more than in the usual case (e.g., as a result of inevitable human fallibility).
It's obviously a particularized inquiry. But, here, I'm happy that Nelson was prosecuted, and think that the result reached by Justice Scotland was the correct one.
Sometimes you can't, in fact, get away with murder. At least forever.