The amulet has no description, and picking it up and wearing it does nothing. You are right in that it might possibly explain why it's evidence if you hand it over to Aureus.
My problem is that not so much that the "dangerous guy gets thrown in jail" solution is only possible by Pickpocketing, but that it's ridiculously obnoxious to try and solve it USING Pickpocketing.
You need quite a bit of Pickpocketing skill to just lift the thing. Probably rank 4 or even 5. (I can't rule out Rank 3, but I doubt that would be enough.) The amulet weighs 0.7 and Pickpocket 2's limit is 0.2.
I CAN'T hand it over to Aureus as evidence because the only way to get it at this stage is to take it from his corpse.
