A man active in several organizations related to Princeton University and its alumni has been charged with possessing child pornography, the Mercer County Prosecutor’s Office confirmed. Roy ‘Trey’ Farmer, 53, faces one count of possession of child sexual abuse material, a third-degree felony. Investigators arrested him Friday at a condo he owns Princeton, across from the university’s main entrance. Farmer was in the Mercer County jail Monday, awaiting a detention hearing court Wednesday in Superior Court of Mercer County in Trenton. A prosecutor’s office spokesperson said the office will argue…