Who is the young man in the sports coat shown on a grainy videotape spilling mercury on a platform of the Red Line subway station at Pershing Square? When it happened on Dec. 22, officials quickly labeled it a harmless accident.

But Thursday, officials acknowledged that the Los Angeles County Metropolitan Transportation Authority botched its response, waiting eight hours after being told mercury was on the platform before clearing the station and cleaning up the spill. Police and transit officials said the workers erred by not immediately contacting law enforcement to cordon off the area and calling in hazardous-material experts. The incident also exposed the fact that many MTA workers are not trained to handle dangerous materials such as mercury.

Several terrorism experts said Thursday that the MTA's handling of the incident was troubling. "It's unnerving, a wake-up call," said USC professor James Moore, an expert in transportation and a researcher with USC's Terrorism Center. "The lesson is that no matter how you slice it, the system isn't prepared to respond adequately. We really don't know what caused this failure, but we need to find out."

Finkelstein and others said MTA workers were caught unprepared by the released mercury because it was a scenario they had not dealt with. "What we need to do is educate all levels throughout our system, whether it's intercom operators or maintenance staff, as well as bus or rail operators," Finkelstein added.