In 2293, Samno, along with Yeoman Burke, participated in the Khitomer conspiracy to sabotage peace talks between the United Federation of Planets and the Klingon Empire. Samno and Burke were on duty in the transporter room when Chancellor Gorkon and his party beamed aboard the Enterprise to attend a formal dinner with Captain Kirk and his crew. After the party had left the transporter room, the two traded racist remarks about the Klingons, Samno commenting "they all look alike."
Following the departure of the Klingon contingent, Gorkon's flagship Kronos One was attacked by a cloaked Bird-of-Prey, suffering severe damage. As the disabled Kronos One drifted out of control, Burke and Samno beamed aboard wearing EV suits and gravity boots, and began systematically murdering Klingons, including Chancellor Gorkon himself. After returning to the Enterprise-A, the pair hid their suits in a ventilation shaft in the ship's officer's mess. However, they accidentally brought aboard some Klingon blood, and their suits were later discovered by Montgomery Scott. When it became clear that the Enterprise-A crew was close to discovering the truth, Burke and Samno were murdered by fellow conspirator Lieutenant Valeris with a phaser set to stun fired at close range.
Later, in a ruse to discover the other conspirator, Captains Kirk and Spock initiated a sting operation, spreading misinformation that Burke and Samno had survived, and then waiting in sickbay to catch Valeris when she came to finish the job of killing the two yeomen. (Star Trek VI: The Undiscovered Country)