BLUEFIELD (UPI) — Mer cer County prosecutor Dav id W. Knight has obtained a court order to exhume the body of one of the three men ac cused in a $300,000 robbery at the home of a Bluefield coal op erator. Knight, who said he had orig inally planned to exhume the body of Ira Mathena on May 18, indicated the action ‘would be taken as soon as it could be arranged with Dr. David Bell, a Bluefield pathologist. Mathena, who was charged with William (Rabbit) Martin and Rufus Raymond of taking the money from the home of C. A. Clyborne, died Jan. 25 in a Bluefield hospital. Knight, who laughed off the theory that the Clayborne mon ey might be found in Mathena’s grave, said the autopsy would be performed to determine the exact cause of Mathena’s death. The first trial against Martin ended in a hung jury Friday and a new trial has been set for Aug. 10. Hampton was the state’s principal witness against Mar tin.