Arthur Coleman, also known as Howard Coleman, is the secondary antagonist in the final Star Trek episode "Turnabout Intruder".
He was portrayed by the late Harry Landers.
A medical doctor, Coleman was at one time a Starfleet officer and chief medical officer on a starship. He was removed from his posting as CMO due to malpractice and administrative incompetence.
Later taking the role of an expedition surgeon on the archaeological survey on Camus II, he helped Doctor Janice Lester murder the other expedition members by withholding treatment for celebium poisoning from them.
When Lester was able to switch her consciousness with that of Captain James T. Kirk, Coleman boarded the Enterprise with her and helped her maintain the illusion of being Captain Kirk to the crew. Dr. McCoy's suspicions were raised when Captain Kirk apparently insisted that Coleman treat the woman who was apparently Janice Lester, due to Coleman's less than stellar history.
Coleman later testified falsely against Kirk at Spock's mutiny court martial.
After the transfer began to fail and the consciousnesses began to return to their original bodies, Lester approached Coleman for advice on how to prevent her return to her own body. Coleman suggested killing Kirk in Lester's body. Before she could kill Kirk the transfer failed, and both Kirk and Lester returned to their original bodies.
At that point Lester suffered a complete mental breakdown. Coleman asked Kirk, McCoy, and Spock for permission to take care of Lester, and helped McCoy escort her to sickbay. He and Lester were taken in to custody for their crimes, with Lester transferred to the Elba II Asylum.