CNN  —  Winning the trust of convicted burglar Jerry Christy was the kind of challenge undercover FBI investigator Ronnie Walker had spent years preparing for. A founding member of the bureau’s specialist Art Crime Team, the Oregon-based agent was well-versed in art history — and trained to pose as a would-be buyer, authenticator or dealer of stolen works. Christy, meanwhile, was being covertly investigated in 2007 over the theft of several artworks, including a 17th-century etching by Dutch