The man who posed as a police officer and raped three women was arrested Wednesday and is expected to be arraigned today. Eric McCoy, 37, of Far Rockaway, a convicted sex offender, is purported to have executed this charade several times this winter. He would approach women on Queens streets in plainclothes, flash a fake police ID and claim to be investigating an assault. On Dec. 4, McCoy took a 27-year-old woman to a motel where he beat and raped her. She later revealed that he had accused her of possessing marijuana. On Jan. 2, he “arrested” a 15-year-old girl and raped her, and then another woman later that day. McCoy is charged with predatory sexual assault, first-degree rape, committing a criminal sexual act, coercion and first-degree criminal impersonation. He faces up to 25 years to life in prison.