How do you get information that’s in a cold case police file on a 25 year old unsolved murder?

I need to know how I would go about finding what’s in a file at the police dept. on a 25 year old murder that is still unsolved. My fiance’ was murdered and his family and I could never get any information out of the police that investigated the homicide. Is there a statute of limitations on holding that information or should we be able to access that information after a certain amount of time? Is there a database we can use to see what’s in the file? Would the FBI FOIA file be of any use?