There has been quite a bit of research on the effectiveness of police lineups and whether presentation of the ‘suspects’ could affect the reliability of the outcome (see here for a huge list of research). One of the big questions is should we show all the suspects together (as above) or is identification more reliable if we present each of the suspects one-at-a-time. In the A2 Psychology of Testimony area we cover aids to recall and recognition and this issue is a very pertinent one.
Much research has provided evidence that this ‘all at once’ approach can have many faults as witnesses expect that the criminal must be there and therefore go for the one that ‘best suites’ the memory of the suspect. With a sequential lineup the witness is not aware of how many people are going to be presented. Each suspect is brought up to the window and the witness must say yes or no. They do not get to go back to look at others again. Some researchers (like Cuttler & Penrod, 1995) have shown this to be a far superior and more reliable way to conduct lineups.
However, a recent report from the US has suggested this might not be the case:
In response to the problems associated with the traditional lineup, pioneering researchers such as Gary Wells spent years developing, researching and testing new lineup procedures. The two major advancements to arise from this thirty year research agenda were The Sequential Lineup, whereby witnesses view suspects one at a time rather than simultaneously; and Double-Blind Techniques whereby the person responsible for the lineup does not know who the real suspect is.
In March 2006, however, a study of an Illinois pilot program, also known as The Mecklenburg Report turned conventional wisdom on its head by claiming that sequential lineups actually result in more false identifications than traditional lineups. [From All About Forensic Psychology]
The Macklenburg report has come under criticism for being methodologically flawed and irresponsible. I have spent a few hours reading several papers which argue both sides of the argument and it seems that most of the research (over 30 years of it actually) supports the idea that sequential lineups are much better – but still police forces around the world are using the conventional ‘all-at-once’ approach.
Read more about this and eyewitness testimony at All About Forensic Psychology.