What makes an eyewitness unreliable

In these cases, witnesses tend to talk to one another in the immediate aftermath of the crime, including as they wait for police to arrive. But because different witnesses are different people with different perspectives, they are likely to see or notice different things, and thus remember different things, even when they witness the same event. The misinformation effect has been modeled in the laboratory. Researchers had subjects watch a video in pairs. Both subjects sat in front of the same screen, but because they wore differently polarized glasses, they saw two different versions of a video, projected onto a screen.

In the video, Eric the electrician is seen wandering through an unoccupied house and helping himself to the contents thereof. A total of eight details were different between the two videos. Four of these questions dealt with details that were different in the two versions of the video, so subjects had the chance to influence one another. Then subjects worked individually on 20 additional memory test questions. Eight of these were for details that were different in the two videos.

That is, subjects allowed their co-witnesses to corrupt their memories for what they had seen. In addition to correctly remembering many details of the crimes they witness, eyewitnesses often need to remember the faces and other identifying features of the perpetrators of those crimes.

Eyewitnesses are often asked to describe that perpetrator to law enforcement and later to make identifications from books of mug shots or lineups. The eyewitness is given a set of small pictures of perhaps six or eight individuals who are dressed similarly and photographed in similar circumstances. If the eyewitness identifies the suspect, then the investigation of that suspect is likely to progress. If a witness identifies a foil or no one, then the police may choose to move their investigation in another direction.

This process is modeled in laboratory studies of eyewitness identifications. In these studies, research subjects witness a mock crime often as a short video and then are asked to make an identification from a photo or a live lineup. Sometimes the lineups are target present, meaning that the perpetrator from the mock crime is actually in the lineup, and sometimes they are target absent, meaning that the lineup is made up entirely of foils.

The subjects, or mock witnesses , are given some instructions and asked to pick the perpetrator out of the lineup. The particular details of the witnessing experience, the instructions, and the lineup members can all influence the extent to which the mock witness is likely to pick the perpetrator out of the lineup, or indeed to make any selection at all.

Mock witnesses and indeed real witnesses can make errors in two different ways. They can fail to pick the perpetrator out of a target present lineup by picking a foil or by neglecting to make a selection , or they can pick a foil in a target absent lineup wherein the only correct choice is to not make a selection.

Some factors have been shown to make eyewitness identification errors particularly likely. It is hard for the legal system to do much about most of these problems.

Memory is also susceptible to a wide variety of other biases and errors. People can forget events that happened to them and people they once knew. They can mix up details across time and place. They can even remember whole complex events that never happened at all. The NIJ's guide, published in , discusses the factors that affect eyewitnesses and provides law enforcement officials with strategies to collect the most accurate information.

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

The speed estimates the students provided were affected by the verb used to ask the question. 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. 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. 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.

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.

It's not uncommon for eyewitnesses to have a poor view of an event. 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. Eyewitness memories can also be malleable. 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. 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.

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

Research has consistently shown that people have difficulty recognizing individuals from other racial or ethnic groups. The "cross-race" effect has major implications for eyewitness testimony and the outcomes of criminal investigations. 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. 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. 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. The feedback a witness is given also makes a difference.

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.

Ever wonder what your personality type means? Sign up to find out more in our Healthy Mind newsletter. Sporer SL. Lessons from the origins of eyewitness testimony research in Europe. Appl Cognit Psychol.

Eyewitness Testimony. Loftus EF. Cambridge, Mass: Harvard University Press; Perceptions and credibility: Understanding the nuances of eyewitness testimony. Journal of Contemporary Criminal Justice. Innocence Project. Gary Dotson. Updated December Updated January Then in, the first person was exonerated through the use of DNA evidence.

DNA evidence has played a big role in proving the unreliability of eyewitness testimony. Memory is not as reliable as we would like to think. Police can plant false memories in witnesses by asking leading questions or using suggesting language. If the police do not follow careful methodology, such as using double-blinds and getting descriptions before showing suspects witnesses, they can alter their memory.

As a result, the witness may accuse the wrong person. This causes problems for not only the wrongfully accused, but also for the police, who may stop pursuing other leads. As well, time plays havoc with our memories. The more time that passes between the event and the retelling, the more the memory tends to change. The most reliable parts of old memories are usually those most pertinent to the person recalling them. So the memory of other people and their appearance can change or fade. In the following video, a classroom experiment shows both the inaccuracy of eyewitness identification.

As well as how easy it is to distort witness memory:. Especially when they see something unfamiliar or under stress. Stress and fear affect our memory.

To do so, it often uses information we receive later.