How confident will you be as a witness in the courtroom?

Imagine that you witnessed a crime scene and were selected as a witness in the courtroom. How confident will you feel about the accuracy of your testimony? What are some factors that might impact your confidence? If you were using substances when witnessing the crime, will you be confident about the accuracy of the witness? 

The field of scientific research has long examined the potential negative impact of using alcohol and other psychoactive drugs during witness on the accuracy of eyewitness testimony. An extensive review suggested that although substance use could influence false memory and suggestibility during testimony, the impact varies depending on the type of substance and when the testimony happens (e.g., during intoxication vs. delay)  (Kloft et al., 2021). For the more frequently researched alcohol and cannabis, both substances increase the susceptibility to false memories and suggestibility when witnesses were highly intoxicated during the crime. This impact still happens after delay and being sober for alcohol users but not for necessary cannabis users. However,  given that there are general stereotypes and untrust about substance-used witnesses in the judicial system and society, it is reasonable to learn more about whether witnesses themselves will not feel confident about their ability to provide testimony and how this impacts the accuracy of the testimony.

A recent review of the confidence-accuracy relationship in eyewitness testimony indicated that existing research generally showed that witnesses’ initial confidence in their first identification is positively related to the accuracy of the testimony (Berkowitz et al., 2022). However, the authors warned that there could be a risk of overstating the power of this “initial confidence” in research, the judicial system, and the press. This is because lab-based eyewitness testimony results are not always generalizable to real-world situations, and jurors tend to rely on witnesses’ confidence a lot in judging their accuracy (Garrett et al., 2020).

A recent study recruited 114 cannabis users to investigate the impact of cannabis use on both the accuracy of eyewitness memory and the confidence–accuracy relationship (Pezdek et al., 2020). Participants were randomly assigned to a control group (being sober) or a treatment group (“high” with cannabis as usual). Immediately after seeing 24 faces for 1.5 s or 5 s each, participants saw a combination of 24 old faces and 24 new faces. For each face, they needed to respond “old” or “new” and rate their confidence in the response. Results showed that the sober group was significantly more accurate in its response than the cannabis group. Even for participants in the cannabis group that reported a high level of confidence, their proportion correct was significantly lower than the sober group. Perhaps most importantly, results also showed that cannabis use negatively reduced the metacognitive judgment of confidence in the cannabis group because only the control group reported more confidence for faces shown for 5 s than 1.5 s. This study indicated that cannabis use during eyewitnesses can at least reduce the confidence and accuracy of immediate testimony.

What happens when witnesses are no longer intoxicated after a while, which is more realistic in an actual courtroom situation? One study recruited 611 participants to watch a crime video and recall the scene either immediately, after one week or after one month (Spearing & Wade, 2021). One month delay was related to lower accuracy and confidence and impaired confidence–accuracy relationship. Given that sober cannabis users are not susceptible to false memories and suggestibility after delay, it will be interesting to investigate whether this result is generalizable to the testimony from cannabis users after a delay period (Kloft et al., 2021). It will also be innovative for research about eyewitness testimony to design lab tasks that better imitate real-world eyewitness and courtroom testimony. 


Berkowitz, S. R., Garrett, B. L., Fenn, K. M., & Loftus, E. F. (2022). Convicting with confidence? Why we should not over-rely on eyewitness confidence. Memory, 30(1), 10–15.

Garrett, B. L., Liu, A., Kafadar, K., Yaffe, J., & Dodson, C. S. (2020). Factoring the Role of Eyewitness Evidence in the Courtroom. Journal of Empirical Legal Studies, 17(3), 556–579.

Kloft, L., Monds, L. A., Blokland, A., Ramaekers, J. G., & Otgaar, H. (2021). Hazy memories in the courtroom: A review of alcohol and other drug effects on false memory and suggestibility. Neuroscience & Biobehavioral Reviews, 124, 291–307.

Pezdek, K., Abed, E., & Reisberg, D. (2020). Marijuana Impairs the Accuracy of Eyewitness Memory and the Confidence–Accuracy Relationship Too. Journal of Applied Research in Memory and Cognition, 9(1), 60–67.

Spearing, E., & Wade, K. (2021). Long Retention Intervals Impair the Confidence-Accuracy Relationship for Eyewitness Recall. Journal of Applied Research in Memory and Cognition, 11.

6 thoughts on “How confident will you be as a witness in the courtroom?

  1. I really enjoyed this post, especially the first paragraph really grabbed my attention on this topic. I also like how you asked the reader questions throughout the post. I think that you explained the studies very well and it was clear to me what was carried out. Something that I would suggest is a larger summary/conclusion at the end just to tie up the facts that you provided to the readers and to close everything off. One more suggestion is to maybe add one more image to help break up the large chunks of reading toward the end of the post. Overall, I thought this topic was very interesting and I would like to learn more about the effects of impairment on memory.


  2. This is a well-done post that covers a very interesting and important topic. I had never considered how substance use would affect eyewitness testimony, or that people who were under the influence during the scene of a crime would be used for testimony at all. I like how you pointed out that knowing how substance use affects witnesses’ confidence is important because judges rely heavily on how confident witnesses are in their reports of the event. You summarized the previous studies in a clear and brief manner, which helped make this an easier read. The last paragraph was kind of confusing to me, as I didn’t quite see how the ideas in that paragraph fit together and the conclusion felt a bit abrupt. Some clear transitions or connections may have helped. Besides that, this is a well-written and informative post!


  3. Hello again! I think you consistently do a good job of bringing people into reading your articles. The topics are interesting, and you explain them well.
    However, I do think that the paragraph between the first two images of this article was worded a little bit unclearly, and it was hard to understand. And I feel as if adding another example in the concluding paragraph made it seem like it was ending very abruptly.
    Other than these two things, I respect how interesting you make these articles!


  4. Such an interesting blog post, Shuran! I’m glad that you wrote about this topic. The reliability of eye witness testimonies is already iffy and adding substance use into that makes it extra iffier.


  5. I really enjoyed reading this post! It is discussing such an interesting topic! I remember learning about how other factors affect witnessing memory in my social psychology class so it is nice to learn how drug plays a role in this. First, I learned that cannabis use during eyewitnesses can reduce the confidence and accuracy of immediate testimony. Second, I learned that a one-month delay was related to lower accuracy and confidence and impaired confidence–accuracy relationship. These two results are really fascinating. However, in the future direction part, I think it would be really nice if you could elaborate a little bit more on those suggestions!


  6. Very interesting stuff! I’ve read a lot about the reliability of those who were drunk but never about those who were high (on cannabis or anything else). It would be really interesting for a study to compare different drugs and their effect on reliability/memory while using and after sobering up. This would be impossible to do because you can’t make people to do hard drugs because its unethical though that’s what I think would be very interesting to compare. I also wonder if it matters what kind of cannabis it is. Sativa, Indica, hybrid, etc., is one kind worse than another for memory reliability?


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