Jev was an Ullian telepathic historian, son of Tarmin. He was trained in the art of telepathic memory retrieval, although he was not as proficient as his father. Tarmin had a large ego and was not ashamed of embarrassing his son in public, generally finding it amusing. As a result, Jev seemed much more introverted and isolated than the rest of the delegation.
Jev spent several years with his father and another Ullian, Inad, gathering memories from eleven planets in eight star systems for use in a large library of memories. During this process, he once spent two days with a contingent of elderly Gentons and was unable to recover anything of substance. Tarmin spent one hour with the group, and retrieved memory fragments from the Gentonian trade wars.
Also during this time, Jev visited Melina II, Nel III, and Hurada III. While on those planets, there were unexplained cases of coma, as well as comas that had been attributed to Iresine Syndrome, which were actually caused by Jev mentally assaulting the victims through telepathic memory invasion, an act Tarmin later described as a "form of rape."
These cases were not solved until 2368, when Jev visited the USS Enterprise-D while en route to Kaldra IV. Counselor Deanna Troi, Commander William T. Riker, and Doctor Beverly Crusher fell victim to comas similar to Iresine Syndrome. The illness was again the result of Jev, who had assaulted each of the officers. He forced each crewmember to recall an incident from their past, usually a disturbing one, and replaced individuals in the memory with himself.
The Ullian delegation was placed under suspicion of bringing some sort of harmful organism or infectious agent aboard, but scans revealed nothing which could cause the comas. Focus then shifted to the telepathic abilities of the Ullians. Tarmin became upset and felt that Enterprise Captain Picard was unjustly accusing the Ullians of wrongdoing and refused to further participate in the investigation. Troi was the first to awaken from her coma, and volunteered to have Jev probe her mind and attempt to discover the cause of the comas. Jev altered Troi's memory to make it appear as if Tarmin was the one responsible for the memory violation, and he was subsequently taken into custody.
When an investigation by Enterprise crew revealed that similar cases of coma were also reported on planets visited by the Ullians, Lieutenant Commanders Data and Geordi La Forge discovered that Tarmin was on the Ullian homeworld when the cases on Nel III occurred. Jev was on that world, leading to the conclusion that Jev was in fact responsible for the comas. He was arrested by Data, Lieutenant Worf, Ensign Kellogg, and another Starfleet Security officer after they burst in and found Jev making a second attempt to telepathically rape Troi, which Worf interrupted by immediately punching Jev.
The Enterprise returned Jev to the Ullian homeworld, where the punishment for his transgressions was expected to be severe. (TNG: "Violations")