A lineup is constructed by placing a person suspected of committing a crime (the suspect) among a collection of innocent people (fillers). An eyewitness is asked to identify the offender from this collection, with a suitable admonition that the offender may not be present. A properly conducted lineup can provide evidence that the suspect is (or is not) the offender or that the eyewitness does not have a reliable memory of the offender's identity. For this to be the case the lineup must not be biased and it must be of sufficient effective size. A lineup is biased when a witness with a poor (or absent) memory is able to guess the identity of the suspect at a rate greater than chance expectation (one per ...