The organization behind the effort to right the wrong is often the Innocence Project.

The New York-based nonprofit was founded in 1992 to help inmates fight wrongful convictions through the use of DNA evidence.

To date, the Innocence Project has helped to exonerate more than 200 people, including 16 who were sentenced to death. Those who have won release spent an average of 12 years in prison.

The success of the Innocence Project has spawned a network of affiliated offices in nearly every major city and state across the country. Offices have also opened in Australia, Canada, New Zealand and the United Kingdom.

With much of the country and several continents covered, there remains a gaping hole right here: Philadelphia is the biggest city in the country without a locally based Innocence Project office.

It's not because of a lack of need. Even without a local office, the Innocence Project has helped free nine people in Pennsylvania and five in New Jersey who were convicted wrongfully.

Nationally, four people have had their convictions overturned this year. Most reversals involve rape, since DNA is most often available.

Many other cases, including murder, don't always produce DNA evidence. As such, scores more are believed to be behind bars for crimes they didn't commit both here and around the country. Most are poor and lack the resources to hire an attorney.

Overturning a wrongful conviction is difficult even with incontrovertible evidence in hand. Mounting a legal challenge often requires smart, dedicated lawyers. Not to mention lots of time, reasonable judges, and fair-minded prosecutors.

The leading cause of the wrongful convictions in the 200 plus cases has been eyewitness misidentification. Other factors include false confessions, forensic fraud, government misconduct, lying snitches and bad lawyers.

All of those issues have cropped up in cases in Philadelphia over the years. That's all the more reason why an Innocence Project office is needed here. In fact, it's surprising the city lacks such an office, given its rich legal history.

Often the office is housed at a law school or a law firm. Most offices require anywhere from $150,000 to $400,000 a year to run, depending on size and office rents. That seems like peanuts, given that what's at stake is a person's freedom or even his life.

The Pennsylvania Prison Society and others have discussed the idea for some time. With the right champion, an office could open quickly.

The need is there. Just ask the more than 200 people who spent years in jail for crimes they didn't commit who have been set free.