Krag was the Tanugan investigator who accused Riker of murdering Nel Apgar and demanded his extradition.
Krag was the chief investigator from Tanuga IV in A Matter of Perspective. After the research station exploded, killing Dr. Nel Apgar, he came aboard the Enterprise and accused Riker of murder. Under Tanugan law, a suspect is guilty until proven innocent.
Krag demanded Riker be handed over, but Picard insisted on a hearing aboard the ship, using the holodeck to recreate witnesses' accounts. Krag's case relied on a beam fired from Riker's location. Data's investigation showed the beam had come from Apgar's equipment, and Krag dropped the charge. Craig Richard Nelson played him.