If you put your backpack down in lower Manhattan and walk away, a “smart” camera may just focus in on it. And if you don’t retrieve it within a few minutes, a bomb squad might storm your knapsack.

More and more “smart” surveillance cameras are being used to identify potential threats in New York City, according to Ray Kelly, the city’s police commissioner. “You can put an algorithm in these cameras” that can spot potential threats like a discarded backpack or large package, Kelly explained.

When a bag was left outside the New York Stock Exchange, Kelly said it was “smart” cameras who alerted the NYPD. The police quickly deemed it a threat and sent out a bomb squad. That bag didn’t contain a bomb, he said, but it’s a prime example of how “smart” surveillance cameras work.

“We have that capability and we’re increasing it,” Kelly said on Monday’s Morning Joe. “The world is changing.”

Sixteen terrorist plots have been foiled in New York since 9/11, he said, and surveillance cameras are a key part of the its efforts. There are as many as 6,000 public sector surveillance cameras in New York City. They prevent crime and help police find suspects, Kelly said, much like how footage of the Boston bombing was instrumental in that ongoing investigation.

Critics argue such cameras invade citizen privacy. The American Civil Liberties Union has been particularly vocal in its opposition, saying that surveillance cameras radically violate privacy.

“By itself, pervasive video surveillance threatens privacy rights. But even more disturbing, the threat multiplies when government combines cameras with emerging technologies,” like the so-called “smart” cameras, the ACLU wrote in its 2007 report Under the Watchful Eye. “It creates the potential for the government to monitor people in public space, in a way envisioned only in futuristic novels,” the report continued. The New York Civil Liberties Union has since begun publicly mapping the locations of surveillance cameras in New York in response.

But Kelly said he believes people are willing to sacrifice their privacy in exchange for more safety.

“The privacy issue has really been taken off the table,” he said. “I don’t think people are concerned about it. I think people accept it in a post-9/11 world.”

Watch the full interview with New York Police Commissioner Ray Kelly below.

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