Prior to 2374, Frane had been arrested four times for harboring violent thoughts, which led to him being classified as a habitual perpetrator. Each time, those violent thoughts were removed by an engramatic purge and Frane spent several years in neurogenic restructuring.
In 2374, he and Guill were part of a black market selling illegal violent thoughts to other Mari. He purposely collided with B'Elanna Torres on the marketplace of the Mari homeworld, so she would have violent thoughts which he and Guill would then steal telepathically. However, since Torres' thoughts were more intense than anticipated they overwhelmed Frane, who later attacked another Mari, the vendor Terril. Initially, Torres was blamed for the incident, but Tuvok was able to reveal the responsibilities of Frane and Guill. (VOY: "Random Thoughts")