Week 2: Initial statements
Before you hear the initial evidence provided by our two eyewitnesses, we’re going to explore some psychological knowledge concerning how accurately eyewitnesses provide different types of information.
Last week you saw that the outcome of an identity parade can be dependent upon the specific wording of the question that is asked of the witness. Simply asking ‘Who is it?’ can imply that the perpetrator is definitely present in the parade and, therefore, that the witness should select someone. The question asked of a witness is an example of a system variable, as it is under the control of the police.
However, there are also estimator variables, not under the control of the police, that are important to be aware of when evaluating witness evidence. Even if you cannot control for how long the witness saw the perpetrator, for example, it is still important to know what affect this might have on the accuracy of their memory.
Knowledge concerning the impact that estimator variables have on eyewitness testimony will be important when you come to evaluate the evidence provided by our two eyewitnesses.