Assess the validity of research into interviewing witnesses

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Making a case
Interviewing witnesses
Assess the validity of research into interviewing witnesses
The aim of witness interviews is to gather as much information which is valid and reliable, and so can be trusted when
establishing what happened at the scene of a crime, or when making a case for or against a suspect.
Loftus et al conducted a study to test the "weapons focus" hypothesis which states that if a weapon is involved in a
crime attention will be drawn away from the face of the offender, making identification harder. Loftus tested this
hypothesis by having two groups of students watch a sideshow of people queuing in a fast-food restaurant. In the
control group the target-customer handed the cashier a cheque, in the experimental group he pulled out a gun.
Participants then answered a questionnaire about the slideshow and were asked to identify the target-customer
from a photo line-up. The results support the weapons focus hypothesis. This experiment was well controlled and had
clearly operationalized dependent variables, which involved the use of scientific equipment which monitored the
gaze of the participants to show where attention was focused. This results in a study which is high in internal validity,
however the lack of ecological validity makes generalizing from this study difficult as surely the effects of weapons
focus would be greatly exaggerated in a real-life situation where fear and stress is added to the equation. Also the
use of students adds to the possibility of demand characteristics, particularly if these are psychology students.
In order to overcome the issue of ecological validity, Yuille and Cutshall interviewed participants who had
experienced a real-life shooting and subjected them to a number of leading questions. Contrary to Loftus' results,
Yuile et al found that participants who witnessed a real-life offence were less likely to be influenced by leading
questions as the trauma of the event presumably embedded the offence onto their memory. This suggests that
studies into weapons focus cannot be conducted in laboratory conditions which lack ecological validity as it
compromises the overall validity of the research.
Fisher et al conducted research into the effectiveness of cognitive interview techniques in gathering more
information from witnesses. His experiment involved training 7/16 serving officers in C.I.T and recording all of their
interviews in the 7 months following their training. A naïve panel of academics were responsible for listening to these
recordings and "counting" the "pieces" of information gathered by both the control group and the experimental
group. Fisher found that the group trained in C.I.T were able to gather 63% more information than the group using
standard interview techniques. However validity issues arise as there is the potential for bias in the "information
counting" process as there is the possibility for verificationism. Also, participant variables might mean that the
officers assigned to the experimental condition were, on average, more experienced and skilled than those assigned
to the control group, which would have further exaggerated the results.
In conclusion, laboratory experiments tend to have a high level of internal validity as they are well designed,
controlled and operationalized and the DV is clearly a result of the IV. However with laboratory experiments comes a
trade-off between control and ecological validity which means that results achieved in the lab are not always
applicable to real life situations (Loftus et al).


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