Posted: December 1st, 2022
Validity of Eyewitness Testimony .
Validity of Eyewitness Testimony
How accurately do eyewitnesses to crimes remember what they have seen? To find out, many researchers have run “crime-simulation studies” in which they show their participants brief videos depicting a crime and then test the participants’ memories for the video. But can we trust this research?
In these studies, we can set things up in just the way we like. We can design the video so that it allows the comparisons crucial for our hypotheses. We can take steps to remove confounds from the procedure and use random assignment to make sure our groups are matched at the experiment’s start. Steps like these guarantee that our results will be unambiguous and informative.Validity of Eyewitness Testimony .
But one thing about these studies is worrisome: The laboratory is in many ways an artificial setting, and it’s possible that people behave differently in the lab than they do in other environments. In that case, the crime-simulation studies may lack external validity—that is, they may not reflect the real-world phenomena that ultimately we wish to understand. As a consequence, we cannot generalize the lab results to situations outside of the lab.
How do we decide whether a laboratory result is generalizable or not? This is an issue to be settled by research, not by argument. As one option, we can draw on the “replication + variation” strategy we discussed in the Research Methods essay for Chapter 5. Specifically, we can see whether we get the same result with different participant groups, different stimuli, different instructions, and so on. If the result keeps emerging despite these changes in procedural detail, we can conclude that the result does not depend on these details in any way. This conclusion, in turn, would strengthen the claim that we can extrapolate from the results to new settings, and new groups of people, including settings outside of the carefully designed research environment.Validity of Eyewitness Testimony .
Another important strategy involves the effort toward making our controlled studies as realistic as possible—for example, using “live” (staged) crimes, rather than videos depicting crimes, or conducting our studies in natural settings, rather than in university laboratories. These steps, on their own, diminish the concern about external validity. In addition, these steps allow us to make some crucial comparisons: Does the effect we’re interested in grow weaker and weaker as our studies become more and more realistic? If so, this is an argument against extrapolating the result to real-world settings. Or does the effect we’re interested in hold steady, or perhaps even grow stronger, as our studies become more and more realistic? This pattern, when we observe it, is an argument supporting the extrapolation from our current data.Validity of Eyewitness Testimony .
Yet another option is quite powerful, but not always available: Sometimes we can collect data from field studies—for example, studies of actual witnesses to actual crimes—and then compare these new data to our controlled experiments. The field studies by themselves are often difficult to interpret. (We obviously can’t arrange a crime to remove confounds from our comparisons, nor can we randomly assign witnesses to one condition or another. This means that the field studies by themselves often suffer from the ambiguities described in earlier Research Methods essays in this workbook.) Nonetheless, we can ask whether the field data are as we would expect, based on the laboratory findings. If so, this increases our confidence that the lab findings must be taken seriously.Validity of Eyewitness Testimony .
How do all of these efforts work out? Are our data, in the end, externally valid? There’s no single answer here, because the pattern of the evidence varies, case by case: Some of our claims, based on lab findings, can be generalized to real-world settings; for other claims, the answer is less clear. Above all, though, let’s emphasize that the broad issue here—and the question about external validity—needs to be taken seriously, and has to be addressed through research. Only then do we know whether each of our claims, initially rooted in controlled studies, can be applied to the real-world phenomena we eventually want to explain.
How can a researcher increase confidence in the external validity of eyewitness testimony based on what is known about memory errors and forgetting?Validity of Eyewitness Testimony .
How a researcher can increase confidence in the external validity of eyewitness testimony based on what is known about memory errors and forgetting
Eyewitness testimony is a vital source of information when doing investigations on what occurred during a crime. Although it plays a crucial role in investigations, it has been established that eyewitness testimony can be unreliable because human memory is frail. As Wise et al (2014) indicate, memories retrieval doesn’t happen in an accurate way and is are vulnerable to falsification. Memory errors might occur at the period of incident or crime, or as a result of what goes on afterward. Post-incident information given by the prosecutors, police, media, family, friends and other eyewitnesses can change the memory of the eyewitness on the crime and also memory of the crime’s perpetrator. Researchers can improve the external validity of eyewitness testimony by understanding human memory and how it works and use appropriate procedures for interviewing witnesses.
Given the view that memory comprises of stored memory cues and traces that are accessible at retrieval, the cognitive interview is an appropriate and well-established approach that can be used for interviewing witnesses. According to Menom et al (2010), during cognitive interviewing the eyewitness is engaged in an in-depth retrieval of the event that he or she originally witnesses. This interviewing protocol comprises instructions from the interviewer that enables the interviewee to remember a prior incident. These instructions are based on two broadly acknowledged theoretical principles regarding information retrieval. First, there is a high likelihood of information being recalled if the context within which the retrieval occurs is the same as the one during encoding. Secondly, it is presumed that there exist a wide range of cues that might enhance memory. Therefore, information that isn’t reachable in one way may be reachable in another way.Validity of Eyewitness Testimony .
The initial instruction of the cognitive interview entails context reinstatement, whereby the interviewer requests the eyewitness to mentally reconstruct personal as well as the physical context that was present when the incident occurred. Menon et al (2010) assert that the second instruction involves requesting the eyewitness to give an account of all things he or she remember even if it seems inconsequential or partial information. the third instruction is to require witnesses to recall the incident from a range of perspectives, including their own viewpoint and adoption of others’ perspectives. Lastly, the witness is instructed to remember the incident again in temporal order or the sequence she or wishes, beginning from the end, middle or the part that he/she recalls most.
Through a cognitive interview, a researcher can build a relationship and communicate with the witness in an effective way. During the process of interviewing, the interviewer should not interrupt the witness and should permit the witness to take control of way the information flows while actively listening to what the witness says. As Lacy and Stark (2013) allege, interviewing must start with the interviewer putting a witness at ease and making them feel comfortable. Witnesses should be requested to mentally reconstruct the crime scene. This is crucial in preventing bias because other people can easily manipulate witnesses.
Testimony must start with a narrative that is open-ended whereby the witness is required to recall events in their own order even when details appear trivial. The witness must be given time to think, relax and collect her or his thoughts. According to Lacy and Stark (2013), permitting witnesses to make reports of incidents at the pace and order they wish leads in a more accurate and more in-depth report. After the free narrative, open-ended questions can be used, with considerations that the way a question is worded can result in distortions of memory. Indefinite articles, rather than definite articles should be utilized. Researchers should also understand that congruency amid numerous eyewitnesses’ accounts doesn’t essentially necessitate more accuracy because there may be communication among witnesses and they are all prone to similar memory errors.Validity of Eyewitness Testimony .
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