Studies of the reliability of eyewitness identifications show little correlation between the accuracy of a witness' s account and the confidence the witness has in the account  Certain factors can increase or undermine witness' s confidence without altering the accuracy of the identification
Ttherefore, police officers are advised to disallow suspect lineups in which witnesses can hear one another identifying suspects
Police officers are more interested in the confidence witnesses have when testifying than in the accuracy of that testimony.