Grady Machnick, a Los Angeles County sheriff's sergeant, and his wife, an elementary school principal, are on trial <a href="http://www.latimes.com/templates/misc/printstory.jsp?slug=la%2Dme%2Dparents21nov21011422§ion=%2Fnews%2Flocal">in an unusual child-endangerment case</a> that may force the justice system to define just where 'tough love' ends and criminal acts begin. They are charged with misdemeanor child endangerment and felony conspiracy for what authorities describe as premeditated psychological cruelty, for which they could face up to three years in prison. The Machnicks said that positive reinforcement failed to correct the behavior of Grady Machnick's son (now aged 16), so they decided to try more serious measures. When the boy failed to clean up after the dogs, Deborah Machnick placed dog feces in his backpack before he went to school. She also took nude photos of him and threatened to plaster them around the school. When the couple suspected their son of stealing cash from them, they forced him to leave the house at 4 a.m. and stay out until the afternoon. Deborah would give the boy additional homework and make him finish it outside. If he didn't, he had to sleep outdoors all night. In a holiday letter sent last year, the couple wrote, referring to their son, 'There are times when parenthood seems like nothing but feeding the mouth that bites you.' Deborah Machnick, who had recently earned a doctorate in education and was known at her school for her efforts at motivating students and boosting their self-esteem, has been moved to an administrative post where she now has no contact with children; while Grady, a supervisor at the Men's Central Jail in L.A., has been placed on unpaid leave.