In most jurisdictions, a plaintiff suing an attorney for malpractice arising out of the attorney's representation in a criminal matter has to meet not only the elements of the cause of action but also has to show actual innocence. This approach has been criticized by many in the literature but it continues to be the majority view.
However, a few days ago, the Kansas Supreme Court joined the minority of jurisdictions where this is no longer the case. In a case called Mashaney v. Board of Indigents' Defense Services, the Court held that a convicted defendant may be able to pursue a legal malpractice claim against his former attorneys without proof of actual innocence.
The Legal Profession Blog and the Chicago Legal Malpractice Lawyer Blog have more on the story here and here.