Interviewing witnesses What do we mean by Weapon’s Focus? How can the weapons focus affect be used to explain poor EWT? What were Pickel’s conclusions? What is a Cognitive Interview? Does it lead to improved EWT?

Factors influencing accurate identification Key study: Loftus et al Aim To provide support for the “weapon focus” effect when witnessing a crime. Method A laboratory experiment.

Participants 36 students at the University of Washington aged 18 to 31. Half were recruited through an advertisement and were paid $3.50 for their participation. The remainder participated in exchange for extra credit in their psychology classes.

Procedure Two sets of 35mm slides were shown. The 18 slides in each series showed people moving through the line of a Taco Time restaurant. In the control group, person B (second in the line) hands the cashier a cheque In the experimental condition, person B pulls a gun All the other slides in both series were identical and shown for 1.5 seconds.

Procedure (cont.) The participants were told it was a study of proactive interference. The dependent variable was measured by a 20 item multiple choice questionnaire. The participants were also given a line up of 12 head and shoulder photos in a random sequence and were asked to rate how confident they were of their identification of person B from the slide series.

Results Answers to the questionnaire about the slide show showed no significant difference between the two conditions. In the control condition, 38.9% chose the correct person B (7 people) against 11.1% in the weapon condition (2 people).

Discussion As expected, the participants spent longer looking at the weapon and therefore had more difficulty in picking the suspect from the line up. In a second experiment with another 80 psychology students using the same procedure the same findings were supported. This influence may be further enhanced in a real world situation when a witness will be more aroused and is likely to have increased attentional narrowing.

The cognitive interview Key study: Fisher et al. (1989) Aim To test the Cognitive Interview (CI) in the field. Method Field experiment with actual interviews of real witnesses by serving police detectives.

Participants Sixteen detectives from the Robbery Division of Dade County Florida. All were experienced with a minimum of five years with the division.

Procedure In the first phase of the experiment, detectives were asked to record a selection of their interviews using the standard interview techniques they normally used. The detectives were then divided into two groups with one being trained on CI techniques. Training was over four, 60 minute sessions. Seven detectives completed the programme and were used in the results which follow.

Procedure (cont.) Over the next seven months more interviews were recorded by the two groups. The post training interviews were analysed by a team at the University of California who were blind to the conditions (trained or untrained in CI).

Results The seven trained detectives elicited 47% more information after training and 63% more information than the untrained detectives. In this field study, accuracy had to be established by corroboration with another source. In 24 cases with corroborating evidence (sixteen by pre-trained detectives and eight by post-trained detectives) 94% of statements were corroborated. The time taken to interview witnesses was not significantly different but CIs do take longer.

Discussion Strong support was obtained for the effectiveness of the CI in the field. More information was obtained from witnesses to real events with no loss of accuracy and a minimal increase in time taken to interview them.