Comment by microwavecamera

Exactly. If someone else gets wrongly convicted for the crime then the actual perpetrator now has no fear of ever being prosecuted for what they did. The fear of being caught for a past criminal act is a deterrence to committing more criminal acts. Once someone else is convicted for that crime, to the criminal, they've gotten away with it. If a novice gambler wins big early, they're more likely to take bigger risks later. The same is true of criminals.