LONDON – Paul Hyland almost never forgets a face. He is a “superrecognizer,” and that is giving an unusual kind of help to his employer: Britain’s Scotland Yard.

Several years ago, for example, London police were on the lookout for a burglar wanted for nine robberies. About a month after seeing the suspect’s picture, Hyland and two colleagues were stuck in traffic.

“I looked up and noticed this guy coming out of a university and knew it was him,” Hyland, 30, recalled, adding that neither of his colleagues had recognized the burglar. Hyland arrested the suspect, who confessed after questioning. “If I’ve met someone before and see them again, I’ll usually know where I know them from, even if I can’t remember their name,” he said.

How does Hyland do it? Nobody knows. But since 2011, about 200 London police officers have been recruited to an elite squad of superrecognizers. Officials say they have tripled the number of criminal suspects identified from surveillance photos or on the street each week, and even helped prevent some crimes, including drug deals, muggings and assaults.

“When we have an image of an unidentified criminal, I know exactly who to ask instead of sending it out to everyone and getting a bunch of false leads,” said Mick Neville, detective chief inspector at Scotland Yard. Neville started the superrecognizer unit after realizing the police had no system for identifying criminals based on images, unlike those for DNA and fingerprints.

The unit proved especially valuable after the London riots in the summer of 2011. Afterward, Scotland Yard combed through hundreds of hours of surveillance video. So far, there have been nearly 5,000 arrests; around 4,000 of those were based on police identifications of suspects from video images.

The superrecognizers were responsible for nearly 30 percent of the identifications, and one officer alone identified almost 300 people. A facial recognition software program made only one successful identification, according to Neville.

Weeks before the Notting Hill Carnival, the biggest street festival in Europe, kicked off last month, the superrecognizers were given images of known criminals and gang members. After the carnival began, 17 superrecognizers holed up in a control room to study surveillance footage and spot potential troublemakers.

Once targeted people were identified, police officers were sent to the scene as a pre-emptive strategy. Neville said that likely prevented some crimes, such as thefts and assaults.

He noted that the superrecognizers aren’t infallible and that their identification is only the start of a case, after which police start looking for other evidence.

Legal authorities warned it could be problematic to use superrecognizers as expert witnesses in court, such as in situations where they identify criminals based on an imperfect image.

“Unless we subject them to (rigorous testing), then we are just taking their word on trust, and we have no reason to do this,” said Mike Redmayne, a law professor at the London School of Economics. “Perhaps they can do what they say, but we don’t have the evidence yet.”

In the United States, experts thought it would be up to individual judges to decide whether superrecognizers needed to be verified before allowing their testimony in court.

David Kaye, a distinguished professor of law at Penn State, said the identification skills of superrecognizers might be analogous to those of sniffer dogs, whose ability to detect drugs are mostly accepted without confirmatory tests. Kaye also noted cases where expert witnesses did not need to have their skills verified before testifying in court and thought that in most instances, the prosecution would have more evidence than simply the identification of an alleged criminal by a superrecognizer.

He said the skills of superrecognizers might be more plausibly used in obtaining search warrants. “There aren’t strict rules for getting a warrant,” Kaye said, explaining that a superrecognizer’s identification of a suspect based on a grainy image might be sufficient to issue a search warrant.

Charles Farrier, a spokesman for the British privacy group No CCTV, called the police’s use of superrecognizers “the latest gimmick” being used to promote the widespread use of surveillance cameras. According to the group, Britain has the most surveillance cameras per person in the world.

But Brad Duchaine of Dartmouth College in Hanover, New Hampshire, a psychologist who has published material on superrecognizers, said he thinks the London police approach makes sense. “People are much better at facial recognition than software (is), so using people is a very reasonable thing to do,” Duchaine said.

Interpol said they are not aware of any police forces worldwide using superrecognizers or similar techniques to London’s Metropolitan Police.

At Scotland Yard’s request, psychologist Josh Davis of the University of Greenwich in England ran several tests on 18 of the best-performing superrecognizer officers and found many scored off the charts when compared to average people. He is now planning to examine all 200 superrecognizers of the London police and to develop a test for new recruits to find who might have special facial recognition abilities.

“We don’t know how (the superrecognizers are) doing it,” he said. Maybe they process facial features more quickly and holistically than other people, he said.

Davis said other police departments in Britain have asked him to test their officers to see if they are superrecognizers, but none have a specialist team just yet.

While most people can learn to remember faces better, scientists say, it is unlikely they could match the powers of a superrecognizer.

“I think some of this is hard-wired,” said Ashok Jansari, a psychologist at the University of East London.

It is like the natural advantage that sprinting champion Usain Bolt holds, he said: “Bolt has a very particular physical makeup that makes him the fastest runner in the world. You could teach other people to use the same techniques he’s using, but they will never be as fast.”

Hyland’s memory for faces is an aberration in his own life. “I’m quite forgetful with basic things,” he said. “I’ll walk into a room and forget what I was coming in for, or I’ll drive to the shops and get a load of stuff except for what I was supposed to get. . . . Like everyone else, I’m not so good with a shopping list.”