This article in The Atlantic Monthly has two simple suggestions for reducing errors in prosecution and jury decisions:

• Record all interrogations on videotape.
• Show only one suspect at a time in police line-ups of suspects.

The second suggestion is especially interesting. Apparently there is a tendency among witnesses to try to choose the person who most closely matches their memory of the person they saw. So why give witnesses with imperfect memories the ability to compare when none of the people in the line-up may be guilty?