Maga Alicia is brought to tribunal by Quaesitor Bertha, who accuses her of killing Quaesitor Carolus in cold blood and outside a proper Wizard's War and asks for her to be Marched. In fact, she also accuses Alicia of not abiding by the results of certamen, of impeding a quaesitorial investigation etc., but points out that if Alicia is found guilty of murder of a fellow maga, the other crimes matter little.
After some heated discussion, the Tribunal reconstructs the following facts, on which both Alicia and Bertha basically agree.
Carolus was investigating some potential Hermetic violation, and this brought him to Alicia's doorstep. After some heated discussion about to what extent Carolus' quaesitorial authority allowed him to pry into Alicia's affairs, the two agreed to fight a certamen. Carolus agreed that if Alicia won, he would leave, stop pestering Alicia, and avoid encouraging anyone else from delving into the issue, including mentioning it to his housemates or anyone else. Alicia in turn agreed that if Carolus won, she would allow him unlimited access to her Sanctum for the next three days, as well as allowing him to cast certain divinations on her.
The certamen was fought with the Arts of Rego and Corpus, and Carolus fairly, if narrowly won; and remained by Alicia's side, guarding her, while she recovered her senses. When Alicia recovered consciousness, she noticed that someone had tampered with her hair. Surreptitiously casting an Intellego spell, she discovered that some of them were now in Carolus' pouch. She immediately demanded them back; but Carolus refused, claiming that he had used the final spell of the Certamen to take them, so he was entitled to them. Alicia then cast a powerful Perdo Corpus on Carolus, empowered by a rook of vis, slaying him.
Bertha says that in the light of these facts the law is very, very clearly against Alicia. Alicia, on the other hand, states that in the light of the same facts, the law is very clearly in her favour. In particular, she says that:
a) The final spell in certamen does not allow a magus to violate the Code. So while it can be used to harm or ridicule the loser, it can't be used to slay him, or deprive him of magical power (see ArM5, p.90), unless that was one of the conditions under which the certamen was fought.
b) Taking an arcane connection through force or deception from an unwilling magus is a serious deprivation of magical power -- specifically, it seriously deprives him of magical defenses against the holder of the connection. It matters not whether no one takes advantage of the lowered defenses, just like dispelling a Parma or an Aegis deprives a magus or covenant of magi of "defensive" magical power regardless of whether anyone takes advantage of the lowered defense.
c) In the face of such an egregious violation of the Oath, Alicia claims she was perfectly entitled to slay Carolus (who had, after all, specifically requested upon taking the Oath that his sodales slay him, should he violate it) to regain the magical power unfairly stolen from her and prevent it from being used for further crimes. In fact, Alicia points out that she should be entitled to a rook of vis from Carolus' legacy in compensation for the rook of vis she was forced to spend to defend herself.
What do you say, sodales?
(One note: please ignore the HP section on the Intangible Assassin for purposes of this discussion. With all due respect to the author, I find it contradicting other sources on a number of issues, and I also find it's not entirely clear on how legal claiming arcane connections by force is).