Most people trust what they see with their own eyes above all else. For the same reason they put great weight on eyewitness testimony. They point to the legal system, which often convicts people of crimes based largely on an eyewitnesses saying "I was at the scene and I absolutely saw the accused commit the crime."
What more do you want? The person was there, he saw who did it, and unless he's a proven liar the case is closed.
Except it's not.
In fact, the New Jersey Supreme Court recently issued new rules to prevent innocent people from being wrongly convicted of a crime based upon eyewitness testimony. According to an article in The New York Times,
The chief justice, Stuart J. Rabner, 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….From social science research to the review of actual police lineups, from laboratory experiments to DNA exonerations, the record proves that the possibility of mistaken identification is real. Indeed, it is now widely known that eyewitness misidentification is the leading cause of wrongful convictions across the country."
The idea that people often incorrectly see, remember, and report what they experience is not merely theory but a proven fact; there are over 2,000 published scientific studies demonstrating it. 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.
The problem of eyewitness unreliability (and memory unreliability) has been known in academia for years; psychologists have long documented how sincere, honest people make important mistakes when reporting what they saw. But it's only recently that the legal system has recognized — and taken steps to mitigate — the problem of eyewitness misidentification.
Consider a few cases that were started (or fueled) by mistaken eyewitnesses.
• When Elizabeth Smart was abducted from her Salt Lake City home in 2002, Elizabeth's sister, Mary-Katherine, watched the abduction while pretending to be asleep, and told the police that the abductor was "about 30 or 40 years old, wearing light-colored clothes and a golf hat." Actually, Smart's abductor, Brian David Mitchell, was wearing black (not white), was nearly 50 (not 30 or 40), and was not wearing a golf hat.
• In 2009, six-year-old Falcon Heene caused a national outcry when his father said he'd been accidentally launched into the skies over Colorado in a homemade balloon. Police weren't sure what to make of the case, whether it was a hoax or a mistake, but what convinced them to take the case seriously was the eyewitness account of Falcon's brother Brad. According to Sheriff Jim Alderman, "He said he saw his brother climb into that apparatus and he was very adamant, they interviewed him multiple times and that was his consistent story." It turned out to be a hoax; the eyewitness was wrong (or he lied).
• When two 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. Checkpoints were set up on roads near the shootings hoping to snare the suspects. The killers were eventually captured: two black men driving not a white box truck but a dark blue Chevrolet Caprice sedan. If the multiple eyewitnesses hadn't got nearly every detail about the killers wrong, the police might have caught them sooner and lives might have been saved.
The research also has implications for other types of eyewitness reports. For example people often report seeing things for which there is little or no hard evidence, such as Bigfoot, UFOs, and ghosts. The bulk of evidence for such "unexplained" reports are eyewitness accounts. Many people who believe in the existence of Bigfoot or extraterrestrials, for example, do so based on the faulty premise that sincere, honest eyewitnesses couldn't be mistaken.
People like to believe that they accurately experience, remember, and understand what they see and hear. We all like to think that we are accurate and observant. Yet the cold hard evidence tells us otherwise; we can all be fooled — every one of us — and if you don't think you can be fooled, you have already fooled yourself.