DETROIT — Patrick Lyoya died of a gunshot wound to the back of head, an independent autopsy conducted by forensic pathologist Dr. Werner Spitz confirmed. Attorneys for Lyoya’s family held a news conference on Tuesday announcing the results of the autopsy that they hired Spitz to conduct. “This is evidence of this tragic killing, which his family believes was an execution,” said Ben Crump, one of the family’s attorneys. Spitz said in a report that Lyoya otherwise had a normal life expectancy, which he estimated would have been about 82 years old. Crump accused the unnamed Grand Rapids police of…