It’s one of the pillars of our criminal justice system but, unfortunately, it’s totally unreliable.
One thing in particular that I recall reading about is the shoddy epistemics of the police lineup. Faced with a group of six dudes standing in a room, your would-be witness points the finger at whichever of the six guys he feels is probably the guilty party. The possibility that the guilty criminal simply isn’t in the room doesn’t “play,” pyschologically speaking. The way the game is understood, the police have caught the criminal. The criminal is in the room. The witnesses role in the game is to correctly identify the criminal the police have already caught. Saying “he’s not here” doesn’t figure into that understanding, so it doesn’t happen, and — bam — you’ve got an eyeball witness to your crime.