HOUSTON -

A man who spent 18 years in prison on a wrongful conviction is now filing a grievance against the prosecuting attorney.

During a news conference Wednesday, Anthony Graves announced the state bar of Texas is investigating whether former Williamson County District Attorney Charles Sebesta is guilty of professional misconduct.

In 1994, Graves was convicted of killing six people.

In 2006, he was awarded a new trial.

In 2010, the case was thrown out for lack of evidence.

Graves was awarded $1.4 million.

Robert Earl Carter was executed for the murders.