What factors can make eyewitness testimony unreliable?

Eyewitness testimony can be unreliable due to conditions at the scene of a crime, memory “contamination” and misrepresentation during trial.

Eyewitness testimony can be an incredibly compelling form of evidence during criminal justice proceedings in Austin. Many people trust eyewitnesses to provide accurate recollections and clear insights into what happened at the scene of an alleged crime. However, despite this perception, research shows that eyewitness testimony is as a top factor in wrongful convictions.

The Innocence Project states that, nationally, over 70 percent of exonerated individuals were initially convicted based in part on testimony from eyewitnesses. This makes evaluating the potential limitations of this testimony critical during any criminal case.

Limitations of memory

Human memory is often viewed as static, but in reality, memories of perceptual experiences are not necessarily fixed. As the National Academy of Sciences noted in 2014 in a comprehensive report on eyewitness testimony, memories may become distorted or degraded when they are initially made or when they are later recalled. Memories may also evolve to accommodate new information. In all of these cases, a person may not realize that his or her memories have undergone any changes.

Environmental factors

When a person witnesses an alleged crime, ambient conditions may prevent him or her from accurately perceiving and remembering what occurred. For instance, if an eyewitness sees an incident in poor lighting or from a distance, his or her recollections are less likely to reliable. A person's biases can affect the accuracy of his or her memories, and so can stress factors, such as the presence of a gun during an assault or violent crime.

Questionable lineup procedures

Even if an eyewitness observes a scene clearly and remembers it precisely, her or his memories may become distorted during poorly managed identification procedures. The information that authorities provide to eyewitnesses, whether deliberately or accidentally, can "contaminate" their memories. Therefore, in its 2014 report, the National Academy of Sciences recommended that authorities avoid the following practices:

  • Allowing police officers who know the identity of the suspect to conduct lineups. These officers may inadvertently give an eyewitness cues that predispose her or him to pick the suspect.
  • Implying that the perpetrator must be present in the lineup. Authorities should instead advise eyewitnesses that the perpetrator may not appear and that the investigation will continue regardless of whether a suspect is identified.
  • Conducting lineup procedures without recording them. A recording can capture any admissions or errors on the part of authorities that may influence an eyewitness's memories and identification of a suspect.

Unfortunately, many practices that can allow eyewitness memories to become contaminated remain widely used, even in cases involving the most serious felony criminal charges. Here in Texas, instructions regarding the presence of the perpetrator in the lineup are recommended, rather than required. Additionally, eyewitnesses are allowed to request that identification procedures not be recorded in certain circumstances.

Misrepresentation during trial

The way that eyewitness testimony is used in trial can also undermine its accuracy. For example, law enforcement authorities may present an identification as certain even if the witness did not express a high level of confidence when he or she made the identification. Similarly, a testifying eyewitness who has received confirming feedback from authorities may have a high level of certainty in an identification that is actually incorrect.

Questioning eyewitness testimony

It is imperative that all of the potential issues with eyewitness testimony be weighed when this evidence is used to support criminal charges. People who face allegations involving eyewitness testimony may benefit from consulting with an attorney for advice on challenging the testimony or otherwise contesting the charges.