LAWRENCE – A former Marblehead man was found guilty Thursday afternoon of twice raping a teenage girl while providing her with alcohol at the Crocker Park in 2009.John Murphy, 24, formerly of 36 Mugford St., Marblehead, was convicted by a Lawrence Superior Court jury of two counts of statutory rape and two counts of furnishing alcohol to a minor.Jurors deliberated for about two and one-half hours before reaching their decision Thursday afternoon.Judge Richard E. Welch III postponed sentencing until Nov. 29 at 9:30 a.m.In the meantime, bail for Murphy was revoked and he was remanded to the Essex County Sheriff pending his sentencing.Assistant District Attorney Karen H. Hopwood successfully presented evidence during the six-day trial that on June 12, Murphy met up with the girl, age 14, provided her with alcohol and then raped her at the Crocker Park in Marblehead.Murphy, who did not testify in his own defense, vehemently denied those charges.Murphy had been living in Stoughton with his grandmother since being released.He faces a potential life sentence on each of the two rape convictions.