Planned New York City subway body scans for weapons draw Fourth Amendment concerns

So strong is the U.S. Constitution’s ban on unreasonable searches and seizures that it took what the courts call a “special needs” exception to the Fourth Amendment — a terrorist attack — to authorize the decades-old policy of randomly searching New York City subway passengers’ bags.

Now, nearly 20 years later, the Adams administration is citing different “special needs” — public safety, when the crime rate is lower than it has been during much of recent city history — to justify a pilot that could begin as soon as late June. It will compel randomly selected passengers to be scanned with a machine in order to enter the subway system. Passengers who refuse won't be allowed to enter through that section.

Under a legally required disclosure document from the NYPD published March 28, if a passenger opts to go through the machine, and the scanner alerts to a potential weapon, an officer will require the passenger to submit to a search of where on his person or possessions the system flags as suspicious.

The plan to force a passenger to submit to a search is “without a doubt” on shaky constitutional ground, said policing scholar Jeffrey Fagan. Particularly relevant, he noted, is the high false-positive rate that showed up in a recent test of the scanners at a public hospital entranceway and a separate probe by federal investigators of the scanners' hit rate in general.

“I think this stretches the boundary of the Fourth Amendment,” says Fagan, a Columbia Law School professor whose research into the NYPD’s stop, question and frisk policies led a federal court in 2013 to declare them unconstitutionally discriminatory. “From what we learned from the stop-and-frisk litigation over the past decade, it’s improbable that a substantial portion of subway riders in New York are carrying weapons in their pockets, so it may be a fig leaf for conducting a more invasive sequence of searches.”

One of the nation’s leading experts on the Fourth Amendment, Orin Kerr, says he is skeptical about the constitutionality of the program — both the scanning and then detaining and searching a passenger based upon the machine alerting. To be constitutional, he said, a program like this needs to have a non-law-enforcement purpose, and "I'm not sure there is one here."

Among the questions a court would ask to determine how legally reasonable the search is, he said: How effective are the scanners at finding actual weapons versus the false-positive rate?

"These are thin lines here, and this is coming awfully close to it. It wouldn't surprise me if a court strikes this down," said Kerr, a professor at the UC Berkeley School of Law.

False positives a concern

While there have been a series of high-profile violent crimes in the subway system — including a train conductor slashed, a shooting on a moving train and passengers pushed onto the tracks, some perpetrated by the mentally ill — crime in the system is lower than it's been during most of the past four decades.

Major crime in the subways is slightly below pre-pandemic lows, but since there are fewer passengers riding nowadays, the per-capita risk is higher.

Although Mayor Eric Adams says the NYPD has not chosen a particular scanning technology to deploy, scanners by Evolv Technologies Holdings Inc. were on display last month at the Fulton Street subway station where Adams announced the pilot and held a demonstration involving NYPD testers. On a nearby computer tablet, a square highlighted where testers were carrying firearms; those with metal objects that weren't weapons were not flagged. 

Evolv scanners already are used at sports stadiums, concert halls, theaters and museums, and Adams says those uses show how beneficial they can be.

Evolv scanners use ultra-low-frequency, electromagnetic fields to detect concealed weapons, paired with artificial intelligence technology that is programmed to distinguish between weapons and benign objects. The company is being probed by the federal government, including the Federal Trade Commission, over claims that the scanners don’t work as claimed.

According to the news outlet Hell Gate, during a test in 2022 of the scanners at the hospital, the scanners alerted to roughly 1 out of every 4 times a person passed through. Of the alarms, 85% were false positives and 14% were law enforcement personnel apparently carrying their service weapons. Just 0.57% were found to be non-law-enforcement personnel with a weapon of some kind.

And weeks before Adams officiated at the Fulton Street subway station demonstration March 28, Evolv's chief executive, Peter George, was quoted in media outlets as saying on an investor call: “Subways in particular are not a place that we think is a good use-case for us.” 

At the demonstration, Adams said: "we're going to do an analysis and determine, you know, 'Hey, is it living up to our expectations?'"

The NYPD did not make anyone available for comment but forwarded a link to the department's disclosure document.

Kristin Parran Faulder, an Evolv spokeswoman, wrote in an email that no one was available to comment but wrote that over 1 billion visitors have been screened since 2019. A scanner subscription can cost about $2,000 per month, depending on the model and other factors, the email said. 

“Our system is trained to err on the side of safety; if an object resembles the components of a weapon, or a weapon could be ‘hidden’ behind an item because of its material makeup, it will alert. Even in that situation, when the alarm sounds, a person can remove the item in question and pass through the system again,” the email said. 

She said results of a test with the NYPD “indicate effective detection performance that align with the city’s current operational goals.” Asked for specifics, she said to contact the NYPD; asked by email for a copy of the results, an unnamed NYPD spokesperson did not provide it.

Crime cited as reason for scanners

The NYPD bag search program has been in place for almost two decades. Civil liberties advocates lost a fight in federal court seeking to stop the program as impermissibly intrusive. The court cited the coordinated suicide attack on July 7, 2005, by Islamic terrorists that killed 52 and injured 770 others in the London transit system.

“New York City's random subway search program, which was begun on July 22, 2005, following terrorist bombings in London's subway system, is constitutional,” the court wrote in upholding the program. “The need for implementing counterterrorism measures is indisputable, pressing, ongoing, and evolving.”

But in greenlighting the program, the court wrote: “The Program addresses a problem well beyond the ‘normal need for law enforcement’ or a ‘general interest in crime control.’”

In March, Gov. Kathy Hochul, citing the need to help the public feel safe from crime and deter it, announced that 1,000 state troopers, MTA police officers and National Guard personnel would help conduct additional bag searches.

Kerr, the Fourth Amendment expert, is also skeptical whether the bag searches for ordinary crime control are constitutional. He cited a 2009 case in which a federal appeals court in Washington, D.C., overturned a police checkpoint set up to deter crime in a troubled neighborhood.

The day of Adams' announcement, Jerome D. Greco, digital forensics supervising attorney for the Legal Aid Society of New York City, condemned the scanning program as misguided, costly and an invasion of privacy.

“The ‘special needs’ exception was for anti-terrorism, not for standard anti-regular-crime. So even if the stats were to show that crime is at an all-time high rate — which it isn’t, as we both know — it still would not meet the special needs exception,” he said last week. 

The NYPD says in the disclosure document that it does not intend on getting court authorization to carry out the pilot.

Chris Dunn, the New York Civil Liberties Union's legal director, who lost the bag-search case, said he has lots of questions about the NYPD’s latest plan to use scanners.

“If the option is, people can walk away before going through the detector, that raises obvious questions about what the security benefit is here,” Dunn said. “I don’t believe they would have any basis for searching people because the detector goes off, given what we know about these detectors.”

Adams has not said at which subway stations the detectors would be placed but said the pilot would begin with a few scanners and could be expanded based on results. According to the document, the plan is for a police supervisor to pick checkpoint locations and frequency of those subject to inspection, such as every sixth passenger, depending on crowd size. The scan could take as long as three seconds.

Will Owen, a spokeswoman for the nonprofit S.T.O.P., the Surveillance Technology Oversight Project, said he is not in theory opposed to scanning for weapons but is skeptical given the high false positive rates and government investigations of Evolv.

“This just really facilitates more unreasonable searches of New Yorkers, and violates their privacy rights,” according to Owen.

The NYPD disclosure document says that “alternative screening” would be available for anyone who needs a medical accommodation, such as for an implanted device like a pacemaker, but the document doesn’t say what that entails.

Evolv’s website recommends that someone with such a device “consult their device manufacturer or physician for information relating to their own specific device.”

“An alternative screening approach is recommended for anyone who has health and safety concerns,” the website says.

The lack of specifics has left people wondering, like 76-year-old Robert Strasser of Massapequa, who got a pacemaker after a bypass operation.

“Gee, for people who have implanted devices, is this safe?” said Strasser, a chief financial officer for an architecture firm.

The legal and medical issues aside, Greco said, he questions whether someone carrying a weapon would be deterred by the scanners.

“People who will see them at one stop,” he said, “will just go to the next stop.”