How do you obtain a official copy of a death certificate?

You can choose to pay for a service to do this, there are many online, just do a search. The other option is to see if your state has court cases available online. In Wisconsin there is a circuit court access page which shows what court cases or charges have been made in wisconsin. It is a really nice site and several other states do the same thing. You can also go to the locality where the person lives and see if there are any cases against them there by going to the local authorities. The reason finding out a person's criminal record is hard is that it is still a person's relatively private business.