(West Linn, OR)  --  West Linn police say they've arrested a man after he responded to an escort ad posted by a police training class on human trafficking.  Authorities say Rene Cruz Mesa of Woodburn was taken into custody after agreeing to meet a fictitious woman for a tryst.  Police say the woman posing as the escort told Mesa to meet her at the address for the West Linn Police Department.  Officials say Mesa was met at the police department by officers, then cited for prostitution and released.