Try to find him first. Google his name. You may be surprised. Send a letter to your state prison system and find out if/when/where he was released. He didn't serve this long for DUI unless someone died and he was convicted of manslaughter.
If all else fails, post an ad in the newspaper of his last known address. Say you are trying to locate him to return property that you are holding, and that failing contact within 30 days you will put the item up for sale. This should cover any legal issues. I AM NOT A LAWYER, but this works for a lot of other legal matters so I would think it would work here.