Just got back from the session that more or less concluded things.
We cheated some stuff to get things moving in stead of dragging it out another seven years to the next tribunal (which was an option).
Basically, the Quaesitores were able to determine the character was responsible. He took an active defence, namely that the Verditious forfit their immunity when they brought the wrath of the mundanes upon their heads.
The Praeco (a Tremere exarch) called the guy into her office and said, "The Q. think this should go to trial. I'm pretty sure if it did it will cost you your life. Give me a reason to help you. And make it good." (She's all about Law & Order, but didn't particularly want to make this mess public.)
He thought hard and long and said, "I'm a good teacher. I can train an apprentice for you."
I thought that was a pretty good offer, and about the only thing he had that she couldn't get somewhere else. (I mean, she'll have an extra soldier in her troop, one likely to have pussant Magic Theory, no less. Although she will have to make sure he's appropriately indocrinated into the Tremere mindset.)
Tribunal concluded and charges were not brought against him. The day after he was brought before the Praeco and the Q. and put on "trial." He was found guilty and lost his familiar (and has to return what he took from the covenant). The Praeco did this because there are a lot of non-covenanted magi in our game who would want the character's head if they found out what he did. This way, if someone does find out what happened, she can say, "Yeah, we found out about it too late to bring it to Tribunal, but we tried and punished him."
And now he's pretty much the Tremere party's toadie, and has to give his apprentice over to them when they ask for it.
All in all, I think I traded up in the story-worthiness of things. He's indebted, involved in politics against his will, and is going to pay for taking that apprentice many times over before all is said and done.