[article] WASHINGTON — The Transportation Security Administration, already under scrutiny after one of its agents was shot to death at Los Angeles International Airport this month, has spent nearly $1 billion on a passenger behavior monitoring program that has not been scientifically proven to work, a key government watchdog agency said Thursday. The Government Accountability Office report was released before a Capitol Hill debate between lawmakers and TSA officials over whether the agency's so-called SPOT program for monitoring people at airports is worth the cost, and whether it should continue for three more years to help identify suspicious people like the gunman who killed one TSA agent and wounded two more as well as a civilian on Nov. 1. "The TSA has limited information to evaluate this program," Stephen M. Lord, a GAO managing director, told a House Homeland Security subcommittee. "They hope it works. But from the GAO's point of view, the program should not be based on hope and faith." TSA Administrator John Pistole strongly defended the $900-million program and urged its expansion, even though it failed to detect and stop the LAX gunman before he opened fire in Terminal 3. "I don't want to take away a layer of security that may identify the next attack," Pistole said.