Last year, at least 87 Americans locked in prison were exonerated. That's the highest annual figure in the past 25 years. We seem to have a problem.

On one hand, it's good that more injustices are being rooted out and fixed. On the other hand, in a perfect system of justice, the number of exonerations per year would be zero. (And if each exoneration caused the system to make real improvements, the number would be going down each year, not up.) Today's report from the National Registry of Exonerations counts more than 1,300 exonerations in the past 25 years. Among the long term trends they discuss:

* Twenty-seven (27) of the 87 known exonerations that occurred in 2013 — almost one-third of the total number for the year — were in cases in which no crime in fact occurred, a record number.

* Fifteen (15) known exonerations in 2013 — 17 percent — occurred in cases in which the defendants were convicted after pleading guilty, also a record number. The rate of exonerations after a guilty plea has doubled since 2008 and the number continues to grow.

* Thirty-three (33) known exonerations in 2013 — 38 percent — were obtained at the initiative or with the cooperation of law enforcement. This is the second highest annual total of exonerations with law enforcement cooperation, down slightly from 2012, but consistent with an upward trend in police and prosecutors taking increasingly active roles in reinvestigating possible false convictions.

Last year, 40 people convicted of murder were exonerated, including one person who'd been sentenced to death. Murder and sexual assault convictions make up the majority of exonerations. The report points out that that may be largely because the meager resources available to review old cases tend to focus on the crimes with the most severe penalties. That would indicate that there may be a whole universe of innocent prisoners convicted of lesser crimes who simply don't have anyone to fight for them. A justice system that relies on after-the-fact exonerations to keep innocent people out of prison is an injustice system.

"Those who were exonerated in 2013 were convicted, on average , more than 12 years earlier; some more than 30 years earlier."

The policy of having prison as our nation's catch-all punishment for everything is not all it's cracked up to be.

[The full report. Image via NRE]