There have been recent movements to review past criminal cases that are "questionable," to say the least, and thus allowing potentially innocent "criminals" out of jail. One prime example of this movement is The Innocence Project, an organization that works towards freeing people who were convicted under wrongful circumstances (more specifically, they contest these questionable cases through DNA testing and evidence).
Criminal exonerations are not exactly common. In fact, in 2013 there were 87 criminal exonerations in the U.S. -- which marks the highest number of exonerations since the 1980s. The 2013 figure also marked a significant increase over 2012, which saw 79 people exonerated. Eight may not seem like a big jump, but when the total figure is this low, it rates as a major victory.
And victory is the right word to use here, because we are talking about people who were locked away (some for years, if not decades) under incorrect pretenses. For example, one man spent more than 20 years in jail for a double murder he allegedly committed. However, it was later discovered that the man was actually in lockup when the crime took place. He was released last year.
While it is nice to see that the justice system is willing to take a look at its own work and correct cases when appropriate (and indeed, the study referenced in our source article credits law enforcement's open mind for the increasing number of exonerations), it is important to stay realistic about exonerations. These don't happen to just anyone. Simply because exonerations are becoming more common does not mean huge numbers of people will be walking out of jail on a technicality.
However, this story does serve as an important reminder that the system doesn't always function perfectly. Law enforcement can make mistakes; evidence can be tampered with or tainted; prosecutors may botch a procedural or clerical aspect of the case, resulting in an accused person walking away free.
Source: Wall Street Journal, "Criminal Exonerations at All-Time High," Jacob Gershman, Feb. 4, 2014