NEW YORK (CBSNewYork) — Security camera video of a slashing attack in Chelsea this week lead to the quick arrest of a suspect and proved what a valuable tool it is to police.

London has the so-called ring of steel, and in Chicago a police partnership with private businesses allows authorities to look at their video in real time.

With security cameras on nearly every street, privacy concerns are being addressed, according to Eric Piza at the John Jay College of Criminal Justice, who researches the use of security cameras.

“Newark, New Jersey police department for example, working off of a national model established out of D.C. actually, consulted with the ACLU while they were in the process of deploying their public cameras,” he told WCBS 880’s Marla Diamond.

Because cameras are nearly everywhere, no one can expect anonymity, but Piza said police take pains to protect privacy.

“Police around the country do go out of their way to make sure that privacy of citizens is maintained,” Piza said.

Privately owned cameras, he says, are another story.

“A lot less is known about exactly how those entities go about maintaining privacy of the public,” Piza said. “Frankly, [it] hasn’t received a tremendous amount of attention from the research community.”

Authorities say security cameras help solve crimes quickly and serve as a deterrent to criminals, but Piza said recent studies of criminal behavior don’t match the claim.

“They report that they don’t feel threatened by cameras because by the time they’ve committed the crime they’re actually out of harm’s view,” Piza said.