How often do murders go unsolved?

Lack of evidence to indicate who is guilty.

Either because the evidence doesn’t exist, because the cops didn’t bother to find the evidence, or because it was pinned on someone else because the cops were too lazy to investigate so they worked for a false confession out of someone else and so the evidence was ignored or never processed.

Edit: fuck me, the question is how often. I read it as like “how can a murder go unsolved”. Attention to detail was ironically lacking