Why did the dallas county district attorney create the conviction integrity unit in 2007?

The Dallas County District Attorney created the Conviction Integrity Unit in 2007 in response to the large amount of cases where there are questions about a convicted person's guilt or innocence, but where there was no DNA evidence to work with. Although these cases take more time to investigate than ones where DNA evidence is available, the Dallas County District Attorney believes it's essential that these cases be addressed.