The Reliability of Eyewitness Testimony

WHY EYEWITNESS TESTIMONY ISNT RELIABLE: Most people think that when police find a "witness" to a crime the case is rock solid. Eyewitness testimony can be extremely powerful. When an independent person sees a crime and testifies under oath, intuition tells us that we should believe what they say. Experienced trial lawyers and the facts, however, indicate that that presumption isn't quite true.


According to a University of Michigan Law school study in the past 25 years, almost 1500 people have been conclusively proven innocent after being convicted of a serious crime. Eyewitness misidentification is the single greatest cause of wrongful convictions. A Project Innocence report reveals that erroneous ID played a role in 72% of convictions overturned through DNA testing. The International Association of Police Chiefs 2006 training guidelines proclaimed that "Erroneous identifications create more injustice and cause more suffering to innocent persons than perhaps any other aspect of police work."

Recent scientific research has identified a number of factors that can lead an eyewitness to make a mistake. Some factors are obvious - bad lighting - distractions, poor eyesight. Other factors are less well known but equally as powerful. Many witnesses are afraid to admit that their courtroom conclusions were influenced by police body language, the desire to please, or stress. In a famous controlled study of numerous store employees, a psychiatrist staged a scenario where a person entered a convenience store and performed a memorable action (like paying in pennies) to test different counter clerks attention to identity. When the clerks tried to pick that person out of a lineup of the clerks that were "certain" they recognized the customer were only accurate 34-48% of the time.


Psychologists have identified what has come to be known as the "weapon focus effect". This phenomenon has become greatly studied in recent years. Numerous studies using eye-focus technology have consistently demonstrated that when a weapon is present in a crime, the weapon draws the witnesses' visual focus away from the perpetrator space. This results in indisputable evidence that witness identifications are dramatically less reliable when the perpetrator uses a gun.

Victims of violent crimes (e.g. robbery, rape, assault) are motivated by a desire to punish someone for hurting them. By the time a case gets to trial, these victims have personified their anger, resentment, and fears into the body of the defendant. The victims have seen the defendant at countless pre-trial hearings and motions. Human nature merges the victim's recollection of the event with the emotional factors surrounding the trial.


I've seen supposed eyewitness trial testimony prove to be inaccurate. Upon cross-examination, witnesses that allege to remember "everything" about a specific attacker, have later admitted being uncertain about his facial hair, clothes, or even race.

The human mind is not like a recording device. People do not record events exactly as we see them, or play them back by pressing "rewind." The unanimous scientific consensus is that a person's acquisition, retention, and retrieval of information is subject to decay, contamination, and distortion. The human mind is susceptible to poor encoding (the poor visibility issues listed above) at the time of initial perception. When a traumatic event occurs a witness has no idea that he will later be asked to recall it under the microscope of trial. As a Cornell Law professor stated, "Human beings are not very good at identifying people they saw only once for a relatively short period of time,.the studies reveal error rates of as high as fifty percent." This is a frightening statistic since many convictions are based solely on one eyewitnesses' testimony.


The legal system is behind the times. In 1967, the United States Supreme Court issued the standard for eyewitness testimony. The Supreme Court stated that the reliability of an eyewitness's identification, and its admissibility, depends in part on the level of certainty that the witness expresses when identifying a defendant in court. Sadly when the Court reviewed photo lineups in 2011 the Court held that as long as an ID was not "procured under unnecessarily suggestive circumstances" a defense lawyer cannot exclude an identification.

This may seem like common sense but psychological study reveals that the court has it wrong. Psychologist have found that when a person identifies a suspect regardless of a witness' level of certainty at the time of original identification the witness' confidence in the correctness of the identification increases over time. Science, however, shows that memory drastically and exponentially degrades over time. The "forgetting curve" of eyewitness memory has been shown to drop off sharply within 20 minutes following the initial encoding. Psychological and cognitive factors such as reinforcement of a witness' beliefs by law enforcement and lawyers cause witnesses to become more certain about events than their recollection justifies. Judges and juries are not made aware of these factors. Judges do not allow lawyers to tell jurors how frequently mistaken identity affects trials.

These problems are easy to fix. First, police should be forced to conduct lineups with the same "double-blind" standards used in scientific testing. The police officer that conducts the lineup should never be an investigator from the case at issue. Next, lineups should be videotaped so that juries can judge how certain a witness appears when she identifies a subject. Third, juries should be told of the statistical problems with lineups. This would make jurors view lineups with a scientifically accurate option of their reliability rather than the false presumption that all independent eyewitness identification are inherently believable.

With these reforms, courts could reduce the number of mistaken eyewitness identifications. Judges and juries could apply a 21st-century understanding to the psychology of witness identification.

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