In his first appearance on the show, he encounters Crichton disguised as a Peacekeeper, and is immediately able to identify him as an imposter (due to his non-Sebacean energy signature) and has him arrested.
In his first appearance on the show, he is portrayed as a walking lie detector. Within seconds of seeing Crichton for the first time, Scorpius identifies him as an imposter (of a Sebacean captain) and has him arrested.