In Michigan you have to hold a Juris Doctor degree, pass the Michigan Bar Exam and be a practicing attorney, then it's recommended to obtain a clerkship under a judge. The clerks are required to do extensive research for the the judge they are under. Michigan judges are appointed by government officials or elected.
I, personally know a judge, who consults specialists for cases and has clerks working under him on civil and criminal cases. Oddly enough, it may seem to some that he makes snap decisions on some cases, but he has so much experience with the type of cases that come before him, it's hard to get anything past him. That being said, he tells me that every case is different.
http://www.ehow.com/list_6779026_requirements-become-judge-michigan.html