WASHINGTON – A pedestrian who strolls through Boston’s Financial District, an area of about 40 city blocks, can be seen by at least 233 private and public cameras.

In the aftermath of the terrorist bombing there on April 15, Boston Police Commissioner Edward Davis wants even more cameras to boost street-level surveillance, said spokeswoman Cheryl Fiandaca. Other cities, too, now may be spurred to expand their systems, which security specialists said will fuel sales growth in the $3.2 billion video surveillance industry.

Such actions increase tensions between law enforcement officials and privacy advocates, who say they worry about Big Brother intrusions into people’s legal activities. The American Civil Liberties Union in San Francisco raised such concerns after Police Chief Greg Suhr cited Boston last week in saying he wants additional cameras for downtown Market Street to give police a better look during parades and other public events.

“We shouldn’t rush into mass surveillance of San Franciscans as they go about their everyday lives,” Abdi Soltani, executive director of the ACLU of Northern California, said on the group’s website.

The role of video surveillance drew national attention as the FBI used law enforcement and private security cameras — plus smartphone images provided by hundreds of people — to identify the suspected bombers, brothers Tamerlan and Dzhokhar Tsarnaev. Since the al-Qaida attacks on New York and the Pentagon in 2001, U.S. cities have deployed video and other sensors purchased with the help of billions of dollars in federal counterterrorism funding.

‘A TERRIBLE REMINDER’

“The Boston bombing is a terrible reminder of why we’ve made these investments — including camera technology that could help us deter an attack, or investigate and apprehend those involved,” New York City Mayor Michael Bloomberg said the day after the attack.

Chicago authorities have access to about 10,000 public and private video surveillance cameras, according to a 2011 report by the American Civil Liberties Union of Illinois. San Francisco has cameras in high-crime areas that are reviewed for evidence after a crime has occurred.

While New York and some other cities have expanded the number of cameras using grants from the Department of Homeland Security, other cities such as Los Angeles have opted against widespread use of cameras, in part because of the cost, said Marc Rotenberg, executive director of the Washington-based Electronic Privacy Information Center.

One law-enforcement ambition is to couple real-time video with artificial intelligence software able to act before a terrorist bombing or other crime occurs. Such systems would alert police to warning signs, such as an abandoned backpack or recognized face, in time to avert a potential terrorist attack.

New York, a target for terrorist plots more frequently than any other U.S. city, is advancing toward that capability with its so-called Domain Awareness System, an effort developed with Microsoft that’s described as drawing real-time information from about 3,000 CCTV cameras and other sensors in lower and midtown Manhattan.

Boston-area authorities had almost 150 cameras in the local network as of 2007, according to the most recent figures provided to the ACLU of Massachusetts. Carol Rose, the group’s executive director, warns against what she considers the temptation to see increasing video surveillance as a solution to the terrorist threat.

“People have to understand there was a lot of surveillance at the finish line of the Boston Marathon,” she said. “Neither there nor in the many studies that have been done is there any evidence that surveillance is going to stop or deter someone from a violent act.”

To the extent that surveillance can help to track a perpetrator, she said “there is no objection to that so long as there are appropriate checks and balances.”

“If we permit our fear to lead us down a path where everyone becomes a suspect, not only are we violating fundamental principles of democracy, but we also are undermining public safety because when everyone is a suspect, then no one is a suspect,” she said.

POLL REFLECTS CONCERNS

Her concerns are shared by many Americans, according to a Washington Post poll after the Boston bombing. The poll found 48 percent of people worry that the government “will go too far” to investigate terrorism versus 41 percent who said the government “will not go far enough.”

Government officials have considerable legal leeway to expand the use of video cameras in public places, said Christopher Swift, a lawyer and an adjunct professor of national security studies at Georgetown University’s School of Foreign Service in Washington.

“Let’s be honest here; the government can fly a helicopter over your house and hover there and take pictures of what’s going on in your backyard, and the Supreme Court has said that is legal,” he said. He was referring to a 1989 case, Florida v. Riley, in which the high court held that police don’t need a warrant to observe an individual’s property from public airspace.

The federal government uses Predator drones to help patrol the border, an area so broadly defined that it includes New York City and Chicago, said Rotenberg of the Electronic Privacy Information Center. U.S. Customs and Border Protection, part of the Homeland Security Department, has outfitted those aircraft with technology to intercept mobile phone signals and identify people on the ground, according to documents Rotenberg’s group obtained under the Freedom of Information Act.

Rotenberg’s organization is seeking to suspend the drone program until privacy rules are put in place.

To the extent drones are used in emergency situations, like the Boston manhunt, “I don’t think anyone is going to object to that,” Rotenberg said. “As a form of routine surveillance 24-7 for the general public, there’s a problem.”