Los Angeles downtown city skyline at night as seen from the Griffith Observatory. (Nathaniel Smith/Flickr)

LAPD Deputy Chief Mike Downing says it makes sense for police officers to play a key role in watching out for any terrorists on the streets of American cities. This attitude reflects a dramatic change in the role of local police departments after the 9/11 attacks.

"There's nobody that knows the landscape better," Downing said. "We're out there seven days a week, 24 hours a day. Communities trust us."

The Los Angeles Police Department now has the second largest anti-terrorism division in the country - after New York.

Downing is the commanding officer of the LAPD's Counter-terrorism and Special Operations Bureau. After 9/11, the number of officers involved in anti-terrorism activities jumped ten-fold, to more than 300.

But Downing says the department trains every cop to keep an eye out for suspicious activity.

"We don't profile people. It's not about the color of their skin or their gender or what country they're from. It's about what behavior are they doing."

That behavior includes obvious criminal behaviors like bomb-making and the production of fake ID's. It also includes taking notes or photographs around high profile buildings.

Some people think police have become too intrusive in their quest to keep America safe.

"I live right in front of the courthouse, and I was just taking pictures," Greggory Moore said.

Moore, who writes for a Long Beach blog, was outside his home taking photographs of passing drivers who were using their cellphones. He was doing a story on distracted drivers.

Eight L.A. County Sheriff's Deputies came out of the courthouse and started questioning him.

"I said 'is it illegal to take pictures of the courthouse?' And he said 'sir step over here.'" Moore said the officers formed a perimeter around him. "I was told to put my hands behind my back palms together and I was patted down very thoroughly." The deputies eventually released him.

Stories like this abound, including one of an artist who was painting a picture of a burning bank. The problem was he was doing it outside a Chase Bank branch in Van Nuys. Police visited him too.

"They've got to train their officers to respect constitutional rights," Peter Bibring of the American Civil Liberties said. Police should not to initiate investigations "based on innocuous or constitutionally protected activity where there's no independent basis for suspicion."

Bibring said officers often collect the names and addresses of people they stop for questioning about potential terrorism. He said he worries how many names have been placed into a national database.

Authorities sought to interview Hamid Khan a few years ago.

"Who knows what kind of file they have on me," he said chuckling.

Khan was head of the South Asian Network in Los Angeles when federal agents tried to question him a couple of years ago. The Pakistani writer refused to cooperate.

"What happens is that lives get disrupted. You have FBI showing up at people's homes, people's neighborhoods, peoples workplaces," Khan said. "People get smeared."

LAPD Deputy Chief Downing says his department is careful to train its officers to follow the constitution.

"I mean there's nothing wrong with a police officer walking up to somebody and having a consensual encounter and asking questions, as long as that person is cooperative," he said.

"I would assume that if the person wasn't doing anything wrong he wouldn't mind."

Civil libertarians say that's a bad assumption for a police officer to make. They say police should not assume someone is a suspect if they are not cooperative.

Downing maintained local police departments should expand their role, not shrink it.

"The threat has really morphed and so we need to adapt and be flexible."

Downing said police agencies need to focus on collecting information on the most pressing threats - Al Qaeda or otherwise.

"Is it violent ideological extremism? Is it white supremacist sovereign citizen movement? Is it black separatists? Is it animal rights? Is it eco-terrorists?" he said. Local police "need to go out and very aggressively and pro-actively collect on those threats."

Downing also reminds people, that the L.A. area, with LAX, the port and many entertainment venues, remains a prime target for terrorists.