SALEM – A Lynn man who was allowed to plead guilty to a reduced heroin charge received 18 months to two and a half years in state prison.Chris Martinez, 39, last known address of 9 Henry Ave., #1, Lynn, changed his plea of innocent to guilty in Salem Superior Court to a charge of distribution of heroin before Judge Howard J. Whitehead.On the late afternoon last July 12 Martinez distributed a small amount of heroin, one finger, to a dealer, who in turn sold it to an undercover officer for $60.Martinez was arrested around 4:30 p.m. at the corner of Franklin and Hanover streets, police said.State Trooper Al Zani spearheaded the arrest.Martinez’ confession to a reduced charge spared him of a mandatory five-year state prison term.He initially was indicted by a grand jury with distribution of heroin, subsequent offenses, due to prior narcotic convictions out of Lynn District Court in 2008 and Fitchburg District Court in 1991.The judge credited him the 367 days he has spent in jail in lieu of $50,000 cash bail following his arraignment.