We don’t know the rule in Montana, but in NY one may not successfully sue his criminal defense attorney without showing actual innocence.  Here is a case from Montana of an exonerated criminal defenendant who wants to sue his attorney, now decesed.  There are of course, many hurdles.  Is there insurance for a public defender?  is there still an estate for the deceased attorney?  Is there a public defender agency?

"A man exonerated of rape charges after 15 years in prison claims in a federal lawsuit seeking damages that he was poorly represented at trial, by a now-deceased court-appointed defender.

Jimmy Ray Bromgard, whose conviction was overturned in 2002, is suing the state of Montana and Yellowstone County for $16.5 million. In depositions reviewed by the Billings Gazette, Bromgard claims his court-appointed attorney, John Adams, advised him to "plead guilty" the first time they met, then mounted a shoddy defense and bungled his appeal.

The public defender program was funded by the county. County attorneys have argued state judges were largely responsible for its operations, the Gazette reported.

Yellowstone County recently made a final offer to Bromgard in an attempt to settle the lawsuit, deputy county attorney Dan Schwarz told the newspaper. Schwarz would not provide further details except to say the offer is open until the end of the year.

The state has filed motions to be dismissed from the case, but they have not yet been ruled on by U.S. Magistrate Judge Carolyn Ostby. That part of the case is expected to focus on allegations of incompetent forensics work by the State Crime Lab and its former director, Arnold Melnikoff. "