I was just discussing the Chaim Weiss case with a friend (my pet case) and we were thinking about how, when you think about it, it's totally possible that even if the police get a tip, and it becomes clear who did it, there might just not be the evidence to convict that person. While I'm sure the police have held back evidence from the press, the impression they give when doing interviews since they reopened the cold case is that they have almost no physical evidence, though given how violent the crime was this surprising me, and this doesn't sound like the kind of crime where it would be easy to compare alibis (seeing as it happened in the middle of the night and a lot of people had opportunity).

What are other cases where the murderer is still likely findable, but it's unlikely the murderer would be able to be proven guilty in a court of law? As in, it's solvable technically speaking- there are people out there who know things that could narrow it down to a particular suspect, and even lead to that suspect's arrest, but too much time may have passed to get the evidence needed to prove their guilt beyond a reasonable doubt.