They hold hands after church, exchange gifts and favors and write each other affectionate letters. In fact, you can call John Hinckley Jr., 30, and Leslie deVeau, 42, mad for each other. The would-be assassin of Ronald Reagan met his newfound steady in a facility for the criminally insane at St. Elizabeths Hospital in Washington, D.C., where both are incarcerated.

Word now has it that the couple is engaged. "The whole hospital could see they were getting involved," says one of their former therapists. "It was love at first sight." At the moment legal authorities believe no law prevents marriage between two such inmates.

DeVeau, a former social worker and onetime member of the Washington society list, went to St. Elizabeths in 1982 after being acquitted by reason of insanity for slaying her 10-year-old daughter with a shotgun. (In a subsequent suicide attempt with the same gun, she lost her own left arm.) Kept in sex-segregated wards, the couple's contact has been minimal—weekly encounters at the chapel, a Labor Day picnic, chats between Hinckley's third-floor window and deVeau's spot in the courtyard below. He has purchased mail-order gifts (a jogging suit and jewelry) for her, and during scheduled social hours they visit in Hinckley's maximum-security ward. Hinckley's parents have acknowledged in their 1985 book, Breaking Points (co-authored with Elizabeth Sherrill), that deVeau was "one of those who have encouraged us through their letters, prayers and expressions of love," and recently they saw their son's sweetie in a hospital-patient visiting room. The couple "are the two wealthiest, whitest people in the facility," said one observer when the relationship became apparent. "I guess they would naturally gravitate toward one another."