Software bug may cause Patriot missile errors

Contrary to what the Post report said, the Patriot cannot function in an automated mode, the expert said.

"There's always a soldier, a man in the loop who makes the decision," he said.

However, information on the Web page of Raytheon, the company that manufactures both the Patriot and its radar system indicates otherwise, listing "automated operations -- including man-in-the-loop [human] override" as a "key feature" of the Patriot system.

A likely scenario has problems with the Patriot's radar combining with human error to result in friendly fire, according to Victoria Samson, a research associate at the Center for Defense Information in Washington, D.C.

"A soldier at the radar might have seen something come in that didn't have a beacon and launched [a missile] before checking," Samson said.

Recent operational testing of the latest Patriot Missile, the PAC-3, revealed software problems, Samson said.

Experts agree that without hard information about the circumstances that preceded incidents on Sunday and Monday, theories on whether software, procedural or human error -- or some combination of those factors -- were to blame are pure speculation.

But those who remember how claims about the Patriot's performance during the first Gulf War were later disputed say that it's reasonable to be skeptical of the claims made by Patriot boosters this time around.

"I hope [the Patriot Missile systems] are doing well. They're certainly vastly improved over the last ten years. Whether they're as reliable as their creators would like them to be? The jury's still out on that," Samson said.