one case in mind where a missing person is almost certainly dead is the oliver mundsen case.
he bought a stolen car from a man, who was then arrested, and oliver would have testified, and shortly afterwards disappeared and has not been seen since.

I agree he probably was murdered no doubt to keep him from talking.

Even though he's dead, I'm sure Oliver's family would like to find his body so that he could be put to rest. I doubt that the police are doing anything to find his body, since so many years have gone by. Very sad.

You are probably right and I dont get the police sometimes and I do think they should keep searching because his family needs closure.

any word on what the criminal is doing these days?

Probably on some beach in Hawaii sipping Martini's, counting the money he's made from selling stolen cars.