Can You Trust Eyewitness Testimony?

Imagine being convicted of a crime you did not commit because a single witness insists that they saw you do it. How is it possible for an innocent person to be found guilty? Is the eyewitness lying? Is it a case of mistaken identity?

Now, imagine that you witnessed a crime. The police have shown you a lineup of photos and asked you to identify the suspect. Could you be 100% certain that the person you think committed the crime is the real perpetrator? How would you feel if you later learned that the person you were certain was the suspect was actually innocent—and that you misidentified them?

Eyewitness testimony has been commonplace in courtrooms around the world and throughout history, but it has a complex place in criminal investigations. Here's what you need to know about how eyewitness testimony works and why its reliability is often questioned.

factors that influence eyewitness testimony
Verywell / Brianna Gilmartin

Definition

In a legal sense, eyewitness testimony refers to an individual's firsthand account of an event that they witnessed (usually one that is suspected to be or considered to be a crime).

An "eyewitness" is typically a victim or bystander who was present at an event that is under criminal investigation (such as a robbery, assault, or murder). "Testimony" is that person's description of what they observed during the event, including those present who were involved in the crime.

While its role is complex, eyewitness testimony is a crucial part of the criminal justice system.

When a legal team presents an eyewitness who can confidently identify the suspect and confirm that they saw them commit a crime, jurors are compelled to believe them.

However, eyewitness testimony has a fatal flaw: It is not always accurate. If a witness provides testimony that is untrue or mistaken, it can lead to a wrongful conviction.

Evidence on the reliability of eyewitness testimony is mixed. According to some researchers, the accounts provided by witnesses are generally reliable. However, the veracity of eyewitness testimony is often called into question because of factors that influence the ability of a witness to accurately recall an event.

Wrongful Convictions

Whether someone saw a car speeding down the street minutes after an accident or they were inside a store when it was robbed, eyewitnesses are often the first source police turn to when gathering information about a crime.

Eyewitness testimony frequently serves as the main lead in an investigation. It can lead to arrests, fuel the interrogation of suspects, and direct the creation of a lineup.

During a criminal investigation, eyewitnesses might be asked to identify a suspect in a photographic or live lineup or give a physical description of the suspect to a sketch artist creating a composite drawing.

If a case goes to trial, witnesses are often asked to appear in court. At times, an entire criminal case is built on eyewitness reports.

Eyewitness testimony can be a prominent and compelling form of evidence in a courtroom. While jurors tend to believe eyewitnesses, these accounts are not as accurate as other forms of evidence, such as DNA.

DNA Evidence

In the 1980s, DNA evidence started to become more widely accessible to police conducting criminal investigations. Instead of relying on the imperfect science of human memory, investigators could use DNA to establish connections between suspects and crime scenes that were more specific and accurate.

The ability to link an individual to a crime through their DNA also allowed for the exoneration of people who had been wrongly convicted. The first exoneration by DNA evidence took place in the U.S. in 1989.

According to the Innocence Project, as of January 2020, 367 convictions have been overturned through DNA exoneration since 1989. Mistaken identification by eyewitnesses played a role in 71% of those wrongful convictions.

A Case of Mistaken Identity

In 1984, a woman named Jennifer Thompson was raped in her home in North Carolina. Thompson escaped the assailant and ran to a nearby house to call for help. The same evening, another woman in Thompson's neighborhood was also sexually assaulted. Police believed that one suspect was responsible for both attacks.

Thompson assisted in the creation of a composite sketch of the rapist, and police assembled a lineup of six suspects. After looking at a photographic lineup of the suspects, Thompson identified Ronald Cotton as the man who had assaulted her.

Later, when asked to identify the suspect in a live lineup, Thompson chose Cotton again, stating, “This looks the most like him.”

The physical evidence only weakly linked Cotton to the crime (including a boot print and a flashlight that appeared similar to one found at the scene). It was Thompson’s identification that served as the main factor in determining Cotton's guilt.

Ronald Cotton was charged and convicted of both rapes, and he was sentenced to life in prison plus 54 years. After serving over 10 years, Cotton was exonerated by DNA testing in 1995 that proved his innocence.

Although Cotton's case is a prime example of their unreliability, eyewitness accounts remain a core component of criminal investigations and legal cases. Eyewitness testimony is still largely believed by jurors and judges despite its faults.

Can Eyewitness Testimony Work?

Some researchers and legal experts insist that eyewitness testimony can be trusted despite the known consequences of inaccurate witness accounts.

However, the insistence often comes with an important caveat: Law enforcement officials must be mindful of how they elicit and respond to information provided by people who have witnessed a crime.

The Importance of Immediacy

The authors of a 2018 study concluded that “eyewitnesses typically provide reliable evidence on an initial, uncontaminated memory test, and this is true even for most of the wrongful convictions that were later reversed by DNA evidence.”

The researchers argued that eyewitnesses are usually correct immediately after a crime takes place, but that their memories become contaminated during the process of interviewing and questioning. Inaccuracies in eyewitnesses' memories can, in turn, lead to wrongful convictions.

The more times an eyewitness is questioned, the more likely it is that their memories will become contaminated.

Being asked leading questions, hearing more information about a case from media or other witnesses, and even having to repeat their story many times can all affect a person's memory.

The Role of Law Enforcement

If an eager witness feels pressured by law enforcement to offer information, they might attempt to fill in the blanks when asked a question rather than admitting that they don't know.

A witness's expectations about what they think should have happened can also influence their memory about what actually happened.

Law enforcement officers can intentionally or unintentionally reinforce witnesses' expectations as they are questioning them.

DOJ Task Force

In 1998, the U.S. Department of Justice (DOJ) created a task force in response to an increase in research on the unreliability of eyewitness testimony, as well as an increase in DNA evidence that revealed wrongful convictions.

Experts on the task force were asked to develop guidelines for law enforcement to ensure that eyewitnesses would not be pressured, unconsciously encouraged, or persuaded to give false statements.

Based on the task force's work, the National Institute of Justice (NIJ) produced a guide book for law enforcement officials outlining the correct way to interview and interact with eyewitnesses.

The NIJ's guide, published in 1999, discusses the factors that affect eyewitnesses and provides law enforcement officials with strategies to collect the most accurate information.

How Questions Are Worded

Eyewitness testimony is not always about identifying the perpetrator. Witnesses may also be asked about the facts of the case. Researchers have found that the words investigators use to gather facts can influence how people respond when asked about the details of an event.

Verb Use

In a classic experiment completed in 1974, researchers showed a group of students seven videos of traffic accidents, each ranging from five to 30 seconds long.

After showing them the footage, the researchers asked all the students the same question but with slightly different wording: “About how fast were the cars going when they [smashed/collided/bumped/hit/contacted] each other?"

The speed estimates the students provided were affected by the verb used to ask the question. For example, when the word “contact” was used, students estimated much slower speeds than when the words “collide” or “smash” were used.

The researchers concluded that eyewitness testimony can be influenced not only by the questions police and investigators ask but also the language they use to ask them.

Invented Details

In a second experiment, the same researchers showed several groups of students a one-minute film that showed four seconds of a multiple-vehicle traffic accident.

When questioning the students later, the researchers used slightly different wording (specifically, different verbs) with each group. Some students were asked, “How fast were the cars going when they hit each other?” while the others were asked, “How fast were the cars going when they smashed into one another?”

A week later, both groups of students were asked if they saw broken glass in the footage of the accidents. Those who had been asked how fast the cars were going when they smashed into each other were more likely to say they saw broken glass—despite the fact that no broken glass was present in the accident.

The researchers concluded that word choice by investigators can potentially prompt witnesses to remember events as being worse than they were in reality. In this way, an investigator's "leading" question might affect how a witness recalls a crime.

Witness Factors

There are also factors specific to the witnesses that can influence what they recall of an event, as well as how they recount the details when questioned by police. While it's not always possible to prevent these factors from interfering, it's important for professionals involved in a criminal investigation to be aware of them.

Poor Eyesight

It's not uncommon for eyewitnesses to have a poor view of an event. Darkness, bad eyesight, an obstructed view, and a large distance between the witness and the action are all factors that can affect a witness’s ability to recall events accurately.

Still, eyewitnesses are generally motivated by a genuine desire to help solve the case. When they attempt to "fill in the blanks" or offer information they are unsure about, it's usually with good (albeit misguided) intentions.

Memory Contamination

Eyewitness memories can also be malleable. An estimated 86% of eyewitnesses claim to have spoken with other witnesses before talking to law enforcement. The conversations lead to what's known as “co-witness conformity.”

When a fellow witness shares their memory of an event, others might be inclined to confirm it. They might say they saw something (or someone) at a crime scene even if they did not. When a witness is uncertain about what (or who) they saw, they can be susceptible to suggestions made by other witnesses.

Memory decay is also an issue with eyewitness testimony. Memories fade with time, and it's not uncommon for months if not years to pass before a case goes to trial.

Stress

Research has shown that the stress and trauma of being victimized or witnessing a crime can also influence an individual's ability to accurately recount the details of an event.

This is especially true when a weapon was used. In these situations, it's common for witnesses to become focused on the weapon rather than the person wielding it.

The "weapon focus effect" gives victims the ability to accurately describe a gun or knife (often in great detail), but leaves them with little to no knowledge of what the perpetrator looked like.

Racial Bias

Eyewitnesses also have preconceived notions about the type of people who commit certain crimes. Consequently, their bias affects how much information they retain about a suspect.

A 2016 study found that witnesses overwhelmingly remembered black suspects’ faces incorrectly when they witnessed crimes that are more often associated with black males, such as drive-by shootings.

Eyewitnesses also remembered black suspects' faces more accurately when they witnessed a crime that is usually associated with other races, such as serial killings.

Witnesses also tend to pair the worst crimes with people with darker skin. A 2016 study called “The Bad is Black Effect” found that when participants were asked to identify perpetrators, they were more likely to choose darker-skinned individuals for more heinous crimes.

For less serious crimes, the witnesses were more likely to point to lighter-skinned individuals.

The Cross-Race Effect

Research has consistently shown that people have difficulty recognizing individuals from other racial or ethnic groups. People struggle to discriminate among faces that don’t resemble their own, especially if they are in a majority population group.

The "cross-race" effect has major implications for eyewitness testimony and the outcomes of criminal investigations.

Research has demonstrated that when a witness is asked to identify a stranger, misidentification is over 50% more likely if they are of a different race.

Suspect Lineups

In the United States, eyewitnesses are presented with a photo lineup and asked if they can identify the perpetrator among the pictures.

Live lineups are also used. In this scenario, the eyewitness is brought in to view the group (usually from the other side of a pane of one-way glass), then asked to state whether the perpetrator is present.

Less often, an eyewitness will be shown a single photo and asked, “Is this the perpetrator?” However, single photos produce less accurate results compared to lineups.

It's not uncommon for an eyewitness to choose the individual that best matches their memory of the perpetrator. This tendency makes it more likely a witness will identify an innocent suspect who happens to closely resemble the real perpetrator.

In an oft-cited experiment, Ray Malpass, PhD and Patricia Devine, PhD staged a crime in the middle of a college lecture. A male actor posed as a vandal, entered the lecture hall, exchanged heated words with the instructor, then knocked over a rack of machines.

When the audience was asked to identify the vandal in a lineup, the accuracy of the witnesses’ identifications depended on the instructions the researchers had given them.

One group of students was instructed to choose among the suspects in the lineup. By contrast, the other group received the message that they did not have to make a choice if they didn't think the suspect was in the lineup.

The suspect was only included in the lineup half the time. The researchers found that telling students that they did not have to choose a suspect led to fewer false identifications. More importantly, the researchers found that being given instruction did not hinder the witnesses’ ability to make a correct identification.

The feedback a witness is given also makes a difference. Studies have shown that when law enforcement officials confirm a witness's choice in a lineup, the witness’s confidence is inflated. However, if police feedback suggests a witness failed to pick the “correct” suspect, the witness's confidence wanes, which can affect future court testimony.

A Word From Verywell

Under the right circumstances, eyewitness testimony can be reliable. To ensure the information witnesses provide is accurate, the people working on a criminal case must carefully examine how witnesses were questioned, as well as the language that law enforcement used to respond to their answers.

Investigators also need to determine whether the individuals providing eyewitness testimony were influenced by other witnesses or the environment around them.

Eyewitness testimony remains a crucial part of the criminal justice system, but it has flaws. The consequences of inaccurate testimony can be serious—particularly if it leads to the conviction of an innocent person.

Jurors, judges, police investigators, and legal representatives need to be educated on the factors that affect the reliability of eyewitness accounts and understand the role eyewitness testimony plays in a criminal investigation.

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