There are many free sites that allow you to find people and find out a lot of information about a person.  By going to radaris.de you can find out other information about the person whose profile you find through the service. There you can find out if the person you know has a criminal record or if he or she has ever been prosecuted. Even if your acquaintance has moved from his previous address and not given it to you, this service will tell you exactly where he is today.