Rayburn was a male Human Starfleet enlisted crewmember in the 23rd century. He served in the operations division aboard the USS Enterprise in 2266 under the command of Captain James T. Kirk, during the historic five-year mission.
That same year, Rayburn was a security guard. When Kirk and Chapel were beamed to the caverns of Exo III, their expectation was that Dr. Roger Korby would be waiting for them. After beaming down and not finding him waiting for them, Kirk requested a security team; the team consisted of Mathews and Rayburn. He was ordered by Kirk to maintain post at an entry point into the caverns.
After losing Mathews, Kirk contacted Rayburn for a status report. He was ordered by Kirk to inform Spock on the Enterprise that a full security party should be on standby and that they would check in at hourly intervals. Conditions set for the security party beaming down was if Rayburn and Kirk lost contact or if Spock failed to hear from either one of them. Before Rayburn could carry out his orders, he was murdered by Ruk by being pushed into a "bottomless" cavern. (TOS: "What Are Little Girls Made Of?")