How long do police keep evidence of crimes?

It’s a question I’ve been wondering for a while, but a recent case has brought it up to my attention again. A man is to be executed sometime next week, I believe, on a rape/murder case. His attourney is pushing for DNA test to be conducted using semen samples found at the crime scene, but the thing is, the murder happened ten years ago.

So how long do police hold onto evidence, especially biological evidence of crimes? There have been other stories of people who have been aquitted after twenty years or so of incarceration that were let off thanks to DNA evidence, but that seems like an awful long time to hold onto a few strands of hair or a few drops of semen. Is there a point where they just clear out the evidence box for a trial, or are there still loads of evidence in storage somewhere for crimes from the 1920s?

I think for a murder case they keep it for a long time. In capital punishment cases they probably keep it until the guy is executed because they know the appeals last a long time. Some states probably have laws requiring it to be kept for a set amount of time.

For lesser crimes I would think they don’t keep it very long past the trial since their storage is limited.

Here in the UK the police are now solving 20 and 30 year old murder and rape cases using DNA evidence on clothing stored as evidence. In one case the murder of three girls in South Wales thirty years ago has just been solved. The murderer had actually died ten years ago and they exhumed his body to get his DNA to get final proof. In another case a man who had spent over twenty years in prison for murder was proven innocent ,again using DNA tests on stored clothing.

It depends greatly on the jurisdiction, the time period in question, and the type of crime. Some PD’s are much sloppier than others.