Sev the Murderer
One of the first things Sev does in BOTNS is kill an innocent man who is fighting to prevent the violation of his dead, who presents no danger to him and with whom he has no quarrel.
"The second volunteer rasied his ax, then hesitated ... he circled to get a clear stroke ... The ax rose; I grasped the helve just below the head almost by reflex, and found myself at once in the struggle, kicking, then striking. Quite suddenly it was over. The volunteer whose bloodied weapon I held was dead."
The context makes it clear that the blood is the "second volunteer's", and that Sev has killed him. Only later does Sev come out and say explicitly that he did so. Perhaps somewhere he expresses some kind of remorse or shows some empathy, but I don't recall it.
Sev does this to protect Vodalus, of whom he knows practically nothing except that he is a grave robber, apparently just because he likes Vodalus' style: " .. it was that willingness [to die] that kindled my admiration for him." And because he is attracted to Thea.
The culminating point of Sev's sham "trial" in Yesod is when he joins battle on the side of the eidolons against the sailors fighting to prevent the destruction of Urth. (UOTN XXI) The eidolons are weak at first, then appear to gain strength as he focuses on them, and when he joins the battle, they triumph at once.
There is a resonance here; once again he takes sides against the real defenders in a cause he knows almost nothing about. He has no idea who the Hierogrammates and Hierarchs really are, or what their agenda is, or how it is to be accomplished. He had meant to question Apheta the night before, but was distracted by sex. At the crucial point, he chooses figments and fantasies over the lives of real people.
This, I believe, was the point of his "trial" - willingness to countenance the death of his fellows in a cause which he does not understand, and which he makes no real effort to understand. But right at the start of his story he demonstrates the characteristics which led to his selection for the role.
(Part of Gunnie's role in the story is I think to give us a viewpoint not infected with Sev's woolly mysticsm. She, like the other sailors, doesn't seem particularly impressed with the Hiero- dudes; should she be, after experiencing Tzadkiel's apparent inability to maintain good order even on the Ship?
At any rate, she calls Apheta a whore. (UOTNS XXIII)
Apheta: "On Urth, women who look as I do, do no work at all - or so I have heard." Gunnie: "Some do.")