Sabin Genestra was the Betazoid investigator who had served as an aide on the staff of Starfleet Admiral Norah Satie prior to her retirement during the 2360s. Sabin's primary role was to both question and authenticate the responses of individuals during interrogations. During their time working together, Satie felt that Sabin's being a Betazoid gave him uncanny instincts that she learned to trust.
Sabin participated in the interrogation of Klingon exchange officer Lieutenant J'Dan, who had admitted to stealing the design schematics for Enterprise's dilithium chamber on behalf of the Romulans, but not to the chamber's sabotage. Sabin confirmed that J'Dan was telling the truth with his admission, which lead to the theory of there being an accomplice.
Sabin would be assigned to the investigation of the Enterprise's crew alongside Lieutenant Worf. Though he felt Worf was very thorough in his work, he was surprised to observe Worf's motivation, after learning of the prior accusations made against his father. When Worf dismissed the accusations, Sabin stated that he "naturally considered" Worf to be a "possible security risk," but assured Worf that he had Sabin's and the Admiral's "complete confidence" and that "you have nothing to prove to us."
Sabin was next present for the questioning of Doctor Beverly Crusher, where he questioned whether there was anything said in her interactions with J'Dan that might further implicate the lieutenant. After Crusher was dismissed, he made the same query to the Crewman Simon Tarses, a medical technician who also interacted with J'Dan. As Tarses was being dismissed from questioning, Genestra, who sensed that Tarses was lying, stating that he was "desperately frightened" and was "covering a lie; one so big it's overwhelming him." Sabin felt that Tarses was the co-conspirator they were seeking, and Satie fully supported her aide in the matter.
In spite of this revelation, Captain Jean-Luc Picard had misgivings about employing a telepath in a criminal investigation, stating that he could not "sanction any action against Mister Tarses based solely on Betazoid intuitions," while lacking better evidence against Tarses. Despite Satie's argument of Picard using Counselor Deanna Troi in similar instances, he still felt "a bit uneasy with this use of a Betazoid."
When it was later revealed that the so-called "sabotage" to the Enterprise was in fact an accident, Sabin found the case "hard to believe" and pressed on in investigating Tarses, even if to establish his "innocence unequivocally." Though working under this subterfuge, Sabin instead focused on his assertion that Tarses' was a liar, and later alleged that Tarses was hiding that he was in fact one-quarter Romulan, rather that Vulcan, and had that the crewman had lied to gain entry into Starfleet.
When Picard was placed under interrogation, for his defense of Tarses, Sabin questioned Picard's loyalty, citing the instance he assisted in delivering a Romulan spy, known to the Federation as Ambassador T'Pel, back into the hands of Romulans. When Worf spoke up for Picard, Sabin then turned on his only ally aboard the Enterprise by questioning Picard's judgment by having a security chief whose father was an alleged Romulan collaborator.
As the trial began to further unravel, and following the departure of Vice Admiral Thomas Henry – an observer to the proceedings – Sabin suggested they go to recess. Following Henry's calling off an further hearings on the matter, Satie and her staff departed the Enterprise. (TNG: "The Drumhead")