How stress affects an eye witness's memory during a crime?

Imagine standing a few feet from a crime. Your heart is racing, your hands are shaking and your brain is desperately trying to make sense of the scene in front of you. Later, after everything has de-escalated, you’re asked to identify the suspect. But what if the very stress that kept you going now makes your memory unreliable and fragmented. This is the reality of countless other eye witnesses. Let’s dive into the psychology behind it all.

The basics of memory

Memory is the process of recalling information that you have learned. Remembering your first day of school would be an example of a memory.  There are different durations of memories namely short-term memory, working memory and long-term memory. Short term memory holds information temporarily, it can last for seconds, minutes or hours. An example of short term memory would be remembering someone’s name right after they have been introduced to you. Working memory is a form of short term memory that allows active manipulation of information by repetition such as repeating a phone number mentally. Long term memory can last for years, it can store information permanently.  An example would be remembering your name. 

How are memories formed and stored

Memories are believed to be encoded by cell assemblies. Cell assemblies is a group of interconnected neurons that fire together in response to stimuli). The strength of these neurons increases when they fire simultaneously enhancing memory retention.

Memory recall and reconsolidation

Memory recall involves coordinated activity across multiple brain regions. Recent research has shown that during recall, synchronised “ripples” of neural activity occur between these regions. Memories must be reconsolidated each time they are recalled. This consolidation phase temporarily makes memories malleable  (easily influenced). Memories can be strengthened, weakened or altered during this period.

How stress affects memory

When stressed, people have a more difficult time creating short term memories and turning those into long term memories. This means that it is more difficult to learn information when stressed. If we are stressed, we have more difficulty remembering the details of the event later. The stress colours our perception as well as our ability to recall what we experienced. 

Weapon focus

Weapon focus is a cognitive phenomenon whereby the presence of a weapon during a crime draws an eyewitness's attention toward the weapon itself, reducing their ability to recall other important details such as the appearance of the perpetrator. The weapon captures and holds an eye witness’s attention because it is a source of threat and high emotional arousal, reducing cognitive resources available for encoding other details, especially facial features. Our memory is vulnerable to distortions, especially under stress or when attention is divided. Research on memory, including weapon focus, has influenced legal systems, particularly leading to the reliability of eye witness identification. Wrongful convictions have often resulted from faulty eye witness testimony.  

Now that we have covered the basics on how memory works, let’s link it to ‘false eyewitness testimonies’. 

Firstly, what is an eyewitness? There are three main types of witnesses that can be present in court. 

1. Expert witness

An expert witness is someone not directly involved with the case, but is qualified to provide knowledge about matters relevant to it. This means they do not experience the case firsthand, but instead just help the judge understand why specific facts are significant. 

For example, an expert witness could be a doctor uninvolved with a medical malpractice case being brought into court to confirm whether or not the doctor on trial acted accordingly. 

2. Character witness

A character witness is someone who is somehow related to either the victim or perpetrator, or someone else important to the case. They are often not very persuasive due to having a bias, but they may present background information on why someone acted the way they did. This can ultimately help with sentencing by humanising the defendant. 

3. Eyewitness

An eyewitness is someone who was present at the scene of the crime and was directly participating in or observing it. This type of witness is the one most commonly seen in the media, and are often the most persuasive. They are the main form of evidence in over 20% of cases, meaning if their testimony is false, it can have large consequences. 

Besides stress, eyewitness talk is another leading causation of memory alteration. This is when multiple witnesses speak to each other after the event and change their mind on what they saw based on what the other person claims to have seen. 

What are the consequences?

The main consequence of inaccurate testimonies are false convictions. This means more actual criminals at large, and innocents in jail. This does not uphold the justice the law intends to provide, and could lead to more crime in the future. 

So, how can we prevent this from happening?

We can’t actually fully prevent false eyewitness testimonies from happening, but we can take measures to reduce them. A few are listed here:

• Prohibiting the eyewitnesses (if there are multiple) from interacting with each other before their testimonies

• Cross-referencing what the witnesses claim 

• Interviewing witnesses beforehand to evaluate their ability to provide a somewhat reliable testimony (eg. if a witness is heavily shaken up, they might still be panicked and accidentally say something false)

• Training lawyers to not ask leading questions

• Educating lawyers on the existence of false eyewitness testimonies so that they are not overdependent on them

• Creating space for uncertainty (eg. the witness may feel pressured to say something just because they feel as though they must help solve the case)

To sum it all up, essentially, basing an accusation solely on the memory of an eye witness is unreliable as the highly stressful situation can make it so a person has difficulty and is less likely to be able to remember the details of the event. Memory can be easily influenced, needing to be reconsolidated to have any use in circumstances which require eye witness testimonies. Weapon focus tends to impact the reliability of eye witness testimonies as the witness often narrows in on the weapon, making their recollection of the perpetrator’s appearance weak. The result of distorted testimonies are false convictions. Examples of ways these could be avoided are cross referencing statements, not pressuring the witness, and not being over dependent on them. To prevent all inaccurate eye witness testimonies is near impossible, however, these measures are key in helping to reduce them.

References

Cleveland Clinic. (2024, September 16). Memory: What It Is, How It Works & Types. Cleveland Clinic; Cleveland Clinic. https://my.clevelandclinic.org/health/articles/memory

Dixon, T. (2019, February 17). Key Studies: “Weapon focus” and its effects on eye-witness memories (Loftus, 1987). IB Psychology. https://www.themantic-education.com/ibpsych/2019/02/18/key-studies-weapon-focus-and-its-effects-on-eye-witness-memories-loftus-1987/

Greshko, M. (2019, March 4). The human memory—facts and information. Science. https://www.nationalgeographic.com/science/article/human-memory

Mojtahedi, D. (2019, May 21). New research reveals how little we can trust eyewitnesses. The Conversation. https://theconversation.com/new-research-reveals-how-little-we-can-trust-eyewitnesses-67663

Rethinking the reliability of eyewitness testimony. (2025, July 23). BPS; The British Psychological Society. https://www.bps.org.uk/psychologist/rethinking-reliability-eyewitness-testimony

Scott, E. (2018, February 12). How Stress Works With and Against Your Memory. Verywell Mind; Verywellmind. https://www.verywellmind.com/stress-and-your-memory-4158323

Team, T. (2021, August 3). Different Types of Witnesses in Court. Tracers. https://www.tracers.com/blog/different-types-of-witnesses-in-court/

The Innocence Project. (2020, April 15). How Eyewitness Misidentification Can Send Innocent People to Prison. Innocence Project. https://innocenceproject.org/news/how-eyewitness-misidentification-can-send-innocent-people-to-prison/

Wise, R. A., Sartori, G., Magnussen, S., & Safer, M. A. (2014). An examination of the causes and solutions to eyewitness error. Frontiers in Psychiatry, 5(102). https://doi.org/10.3389/fpsyt.2014.00102