The Massachusetts State Police says it can't locate most departmental emails sent before 2018, and that may put into jeopardy payroll fraud and larceny charges against a former trooper. An attorney for David Keefe has asked a court to dismiss charges against his client because the police turned over only about 4,500 of an estimated 34,000 emails Keefe says would show he was working when prosecutors say he was absent but on the clock. Keefe is one 20 troopers charged with overtime fraud. The agency blames a change in email programs for the loss of the emails. But outside experts note that Keefe and other troopers were under investigation at the time of the switch, which placed a legal obligation of the agency to maintain evidence in the case.