How reliable is eyewitness testimony?
Psychologists are helping police and juries rethink the role of eyewitness identifications and testimony.
By Zak Stambor, Monitor Staff
April 2006, Vol 37, No. 4
On Oct. 10, 1997, Fairbanks, Alaska, residents who had lived in the state at least a year received about $1,500-an equal share of the income produced by the sale of state's oil and other natural resources. Residents receive these oil dividends, in part, to keep them vested in their state government.
Inevitably some residents raucously celebrate the annual windfall, and that night the celebrating turned deadly as four young hooligans embarked on "Clockwork Orange"-style attacks on random individuals. When the night was over, a teenage boy, John Hartman, had been robbed, sexually assaulted and murdered, and an older man, Franklin Dayton, was seriously injured after being robbed and attacked.
Within days, four suspects were arrested and locked up. At the trial two years later, the prosecutor's case rested on an eyewitness account by Fairbanks resident Arlo Olson, who testified that as he stood in the doorway of Eagles Hall, he watched in horror as a group of men, whom he identified as the defendants, accosted and savagely beat Dayton in a parking lot 450 feet away.
"No physical evidence actually ties any of the defendants to the crimes," wrote Fairbanks Daily News-Miner reporter Larry Campbell in an article on the trial.
The defense called as an expert witness Geoffrey Loftus, PhD, a University of Washington perception and cognition psychology professor who testified that Olson was too far away to accurately perceive the defendants' facial features. Seeing someone from 450 feet away is like sitting high in the center field bleachers in Yankee Stadium and looking across the ballpark at another individual sitting in the stands behind home plate, Loftus testified.
Despite Loftus's testimony, the jury convicted the defendants of assault and murder. Four years later, the defense attorney learned that the jury had believed Olson's identification because four jurors had conducted an illegal and unauthorized experiment in broad daylight: They paced out what they thought was 450 feet. And once one juror suggested that she could see clearly, it negated Loftus's testimony, the defense attorney said. As a result, the conviction was sent to an appeals court where it remains in litigation.
Mistaken or flawed identification has assumed a newfound prominence in recent years: It's been cited as a factor in nearly 78 percent of the nation's first 130 convictions later overturned by DNA testing, according to the New York-based Innocence Project, which works to free the wrongly convicted. As a result, a number of researchers are turning their attention to helping police departments and juries better understand the circumstances under which eyewitnesses observe crimes and later identify a suspect.
Distance creates blurriness
Soon after testifying in the Fairbanks trial, Loftus began seeking a way to visually present to juries the proposition that people's ability to decipher details degrades rapidly as a person or object moves further away.
"At 10 feet, you might not be able to see individual eyelashes on a person's face," he says. "At 200 feet, you would not even be able to see a person's eyes. At 500 feet, you could see the person's head but just one big blur. There is equivalence between size and blurriness-by making something smaller you lose the fine details."
In a 2005 article in the journal Psychonomic Bulletin & Review (Vol. 12, No. 1, pages 43-65), Loftus examined his distance-as-filtering hypothesis that, as a face moves further away, its details become progressively courser and more difficult to recognize.
In the study, Loftus and Erin Harley, PhD, a postdoctoral fellow at the University of California, Los Angeles, conducted a series of experiments with participants who had 20/20 vision or corrected 20/20 vision. They presented participants with small, unrecognizable images of famous people like Julia Roberts, Michael Jordan and George W. Bush, and gradually enlarged the images until the participants could identify each person. The researchers then recorded the size at which each participant recognized the celebrity and then converted this size to a corresponding real-life distance. In another part of the study, Loftus and Harley started with blurred images of the celebrities and then gradually clarified them until the participants could recognize them. The researchers then recorded the amount of blurring that the made the face recognizable.
Comparing the relationship between losses in clarity due to size or blurriness allowed Loftus to develop a formula to approximate the amount of detail people who have 20/20 vision lose at a range of distances in normal daytime light.
"We know enough about the visual system that we now can create a visual depiction of what is lost at any given distance," Loftus says. "When an image is far away, the image shrinks in size on the retina and, as a result, loses details."
The formula, Loftus says, allows expert witnesses-like himself-to use a specific mathematical relationship between image quality and distance to visually simulate the conditions under which an eyewitness observed a crime.
"As an expert witness, my aim is not to use absolute judgment, but to provide as much information as possible," Loftus says. "This tool provides a visual aid to show a jury the best possible view that a witness might have had."
A new spin on eyewitnesses
Iowa State University experimental social psychologist Gary Wells, PhD, a member of a 1999 U.S. Department of Justice panel that published the first-ever national guidelines on gathering eyewitness testimony, says Loftus's model suggests that crime investigators need to think about eyewitness evidence in the same way that they think about trace evidence.
"Like trace evidence, eyewitness evidence can be contaminated, lost, destroyed or otherwise made to produce results that can lead to an incorrect reconstruction of the crime," he says. Investigators who employ a scientific model to collect, analyze and interpret eyewitness evidence may avoid incidents like Olson's potentially flawed identification of the Fairbanks suspects, he notes.
In fact, Wells says that other evidence techniques, such as police lineups, are similar to scientific experiments. In lineups, the police have a hypothesis, they provide instructions, collect responses and interpret the results. As such, the same factors that can bias the results of an experiment can bias an eyewitness's performance in picking suspects out of a lineup, he says.
In a 2000 American Psychologist (Vol. 55, No. 6, pages 581-598) article that dovetailed with the Department of Justice report, Wells and his colleagues outlined a number of ways police can avoid biasing eyewitness testimony, including warning the witness that the actual perpetrator may or may not be in a lineup, maintaining a double-blind lineup environment so that a detective cannot influence a witness's judgments and securing a statement of the witness's certainty of their identification.
"To a research psychologist, the changes seem obvious," he says. "But to law enforcement officials they are very different from how they've tended to do things in the past."
Since the publication of both the American Psychologist and Department of Justice pieces, states such as New Jersey, North Carolina and Wisconsin have incorporated many of the recommendations, including one in the Department of Justice report that advises law enforcement officials to warn eyewitnesses that the culprit's appearance may have changed since the crime.
However, Wells challenges that recommendation in an upcoming article in Law and Human Behavior. In the study, he presented participants with a video of a crime involving four culprits. Then, he asked the participants to identify the culprits from four six-person arrays that either included or did not include a culprit. He found that the instruction actually increased the participants' number of misidentifications.
"The instruction seems to loosen the criterion of eyewitnesses and increases their propensity to identify someone," he says. "Eyewitnesses start to imagine possible changes and think, 'This must be him.'"
Wells is optimistic that such psychological research can have a profound impact on both police's evidence-gathering practices and on how courtrooms inform juries-like the Fairbanks jury-of the possibility that flaws may exist in eyewitness accounts.
"The system [of interpreting eyewitness accounts] will never be perfect, but psychological research can help make it a lot better," he says.