"Inside the courtroom, witnesses ordinarily have no trouble figuring out who to identify: it's the person sitting next to the defense attorney. Arranging for a truer test of an eyewitness' credibility, famed defense lawyer Johnnie Cochran Jr., on at least one occasion got a judge to allow the defendant to be seated among the spectators. A decoy sat next to Cochran at counsel table. When the eyewitness was asked to 'look around the courtroom and tell us if you see the perpetrator,' the arrangement forced the eyewitness to carefully consider before answering.
Much earlier in the 20th century, legendary Los Angeles lawyer Earl Rogers did the same thing, actually having the defendant switch places with a courtroom spectator while Rogers cross-examined the eyewitness. Rogers stood so as to block the witness' view of the switch." -From, "The Criminal Law Handbook"