He's been on death row for 22 years. Why he may be innocent.

Robert Roberson has been scheduled to die three times. In 2003, Roberson was convicted of capital murder for the death of his two year old daughter, Nikki. Prosecutors argued that the blunt force trauma to her head was caused by someone shaking her. Roberson has been in prison ever since. If the Texas Attorney General gets his way, Roberson will be the first person in US history put to death for a case of shaken baby syndrome. But a growing number of advocates, including the detective who arrested him, say the state would be killing an...