Updated

A store clerk's curiosity about why Najibullah Zazi was buying large quantities of beauty supply products indicated that something about the transaction wasn't quite right — and it's an example of the kind of citizen vigilance that can combat terror, a police commander said Saturday.

Los Angeles police Cmdr. Joan McNamara cited this summer's incident as police chiefs meeting in Denver adopted a model for a nationwide community watch program that teaches people what behavior is truly suspicious and encourages them to report it to police.

Federal authorities allege Zazi, 24, tried to make a homemade explosive using ingredients from beauty supplies purchased at Denver-area stores. He has been jailed in New York on charges of conspiracy to detonate a weapon of mass destruction in a plot that may have targeted New York City. Zazi has denied the charges.

Los Angeles police Chief William Bratton, who developed the iWatch program with McNamara, called it the 21st century version of Neighborhood Watch.

The Major Cities Chiefs Association, headed by Bratton and composed of the chiefs of the 63 largest police departments in the U.S. and Canada, endorsed iWATCH Saturday at its conference in Denver.

iWATCH would have provided a way for that Colorado store clerk and others to report suspicious activity to police and possibly launch an investigation earlier, McNamara said.

"That clerk had a gut instinct that something wasn't right," he said.

Using brochures, public service announcements and meetings with community groups, iWATCH is designed to deliver concrete advice on how the public can follow the oft-repeated post-Sept. 11 recommendation, "If you see something, say something."

Program materials list nine types of suspicious behavior that should compel people to call police, and 12 kinds of places to look for it. Among the indicators:

—If you smell chemicals or other fumes.

—If you see someone wearing clothes that are too big and too heavy for the season.

—If you see strangers asking about building security.

—If you see someone purchasing supplies or equipment that could be used to make bombs.

The important places to watch include government buildings, mass gatherings, schools and public transportation.

The program also is designed to ease reporting by providing a toll-free number and Internet Web page the public can use to alert authorities. Los Angeles put up its Web site this weekend.

"It's really just common sense types of things," Bratton said, adding that his department is providing technical assistance to other agencies that want to adopt the program.

But American Civil Liberties Union policy counsel Mike German, a former FBI agent who worked on terrorism cases, said the indicators are all relatively common behaviors. He suspects people will fall back on personal biases and stereotypes of what a terrorist looks like when deciding to report someone to the police.

"That just plays into the negative elements of society and doesn't really help the situation," German said.

After the Sept. 11 attacks, the Bush administration proposed enlisting postal carriers, gas and electric company workers, telephone repairmen and other workers with access to private homes in a program to report suspicious behavior to the FBI. Privacy advocates condemned this as too intrusive, and the plan was dropped.

Bratton and McNamara said privacy and civil liberties protections are built into this program.

"We're not asking people to spy on their neighbors," McNamara said.

If someone reports something based on race or ethnicity, the police will not accept the report, and someone will explain to the caller why that is not an indicator of suspicious behavior, McNamara said.

The iWATCH program isn't the first to list possible indicators of suspicious behavior. Some cities, like Miami, have offered a public list of seven signs of possible terrorism. Federal agencies also have put out various lists.

Other efforts encourage the public and law enforcment to report such signs through dozens of state-run "fusion centers" across the country. One such center, the Colorado Information Analysis Center, has a form on its Web site to report suspicious activity.

Bratton hopes the iWATCH program becomes as successful and as well known as the Smokey Bear campaign to prevent wildfires.

"There he is with his Smokey the Bear hat, similarly here, we hope that this program, even though it's in its birthing stages right now, in a few years will become that well know to the American public."