In the two weeks since David Sweat and Richard Matt made a dramatic escape from the Clinton Correctional Facility many people have contacted police to report having seen them. The manhunt is focused on Western New York and Pennsylvania, though last week officials said the pair could be as far as Mexico.

News media have reported on dozens of “credible sightings” by the public and of course for every credible sighting there are many non-credible sightings.

According to USA Today, “On June 13, witnesses spotted two men walking near a rail yard in Erwin, N.Y., New York State Police said late Friday. The next day, men who matched that description were seen walking along a road in Lindley, N.Y., heading toward the New York-Pennsylvania border.”

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Whether the two men were Sweat and Matt remains unknown. Here’s a typical sighting described to The New York Times: “She saw two men. It was a glimpse, maybe a few seconds. One pulled the hood of his sweatshirt over his head, and she could see the other man only from behind. Nevertheless, she saw enough to make her think it could be the killers who have been pursued by law enforcement since their escape from a New York State prison well over 300 miles from here.”

All of this has implications for psychology and eyewitness reliability; if you tell people what to look for, any face or physique that is even remotely similar (large black male, small blonde girl) can become a (false)-positive identification. Until Sweat and Matt are apprehended, it’s likely that any two unknown males seen from a distance in the areas being searched will be regarded with suspicion.

Mistaken Identities

Police routinely use the news media to help find suspects, fugitives, and missing persons. That’s the idea behind circulating photos of suspects and issuing Amber Alerts: to use the general public as the eyes and ears of law enforcement.

But it’s a double-edged sword: while the public can indeed be helpful in finding people (Elizabeth Smart, the girl abducted from her Salt Lake City home in 2002, was recovered nine months later after she was recognized by a couple on a street who called police), it also generates hundreds of false tips and sightings. Police, of course, must treat all sightings and reports as potential leads; ignoring a valid tip might cost lives.

Contradictory eyewitnesses are a well-known problem to psychologists and police detectives. Though the general public often puts great credence in seemingly irrefutable first-person eyewitness accounts, errors in perception and memory can and do influence recollections. In 2011 the New Jersey Supreme Court issued new rules to prevent innocent people from being wrongly convicted of a crime based upon eyewitness testimony.

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The chief justice wrote in a unanimous decision that the legal system had to catch up with scientific evidence in order to ensure justice. “Study after study revealed a troubling lack of reliability in eyewitness identifications,” he noted. By some estimates, as many as one-third of eyewitness identifications in criminal cases are wrong, and nearly 200 people who were convicted of crimes based on positive eyewitness identifications were later exonerated through DNA evidence.

When a pair of snipers terrorized the Washington, D.C. area in October 2002, killing 10 people and injuring three others, the nation’s capital was paralyzed. Police caught a break when eyewitnesses reported seeing the shooters: Two white men in a white box truck. Police set up checkpoints on roads near the shootings, stopping white men in white trucks.

Yet the killers turned out to be two black men driving a dark blue Chevrolet Caprice sedan. Several eyewitnesses had gotten nearly every detail about the killers wrong, causing police to focus on the wrong suspects and possibly costing innocent lives.

One famous search spawning false sightings occurred in 2007 when 3-year-old Madeleine McCann disappeared from a resort in Portugal. Her presumed abduction made international news, and photos of McCann circulated widely as police and the girl’s family hoped for tips from the public. This led to McCann being “sighted” in dozens of countries on different continents around the world. None of the sightings turned out to be true and eight years after McCann’s disappearance she remains missing.

Dangerous Misidentifications

Misidentifications not only waste police resources but can also be potentially deadly. During the 2013 manhunt for California police officer killer Christopher Dorner, wanted in connection with a series of shootings that killed four people and wounded three others, the public was asked to report possible sightings.

Hundreds of tips came in from people in the greater Los Angeles area reporting false sightings of the fugitive. Police officers descended on a Kentucky Fried Chicken outlet in Tarzana, arresting an innocent African-American man who barely resembled Dorner. Dorner was later “seen” at a Lowe’s home improvement store in Northridge (causing a SWAT team to be dispatched), and also at Men’s Central Jail in downtown Los Angeles, and elsewhere.

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In fact all the Los Angeles sightings turned out to be wrong; Dorner was actually in the San Bernardino Mountains where he shot himself after being surrounded by police.

In several cases police officers drew their weapons and fired upon people who were mistaken for Dorner. A lawyer for two women who were injured (one of them a 71-year-old woman shot twice in the back) told the Los Angeles CBS affiliate that the mistaken identification wasn’t even close: “The vehicle is a different color. The license plate doesn’t match. There’s nothing there for you to start shooting people.” The Los Angeles Police Department later paid the victims $4.2 million for their injuries.

Though a few sightings reported to police are hoaxes done for attention, most reports are made by sincere people. The promise of reward money may also encourage citizens to contact police with dubious reports; there’s now a $100,000 reward for information leading to the capture of Sweat and Matt.

People who might otherwise be reluctant to call police based on nothing more than a mild hunch or fleeting glimpse have a lot to gain and nothing to lose by reporting their sighting.

Late news suggests that a DNA match to one of the men may have been found, and it seems likely that Sweat and Matt will be captured soon—hopefully before any innocent people are endangered by mistaken eyewitnesses.