Upright Trait: How does it progress ?

[Shahed]

Hey !

The Upright trait... Honest -> Trustworthy -> Utterly Immaculate, which gives +6 Law. I'd like to know how to influence this trait to progress on one of my generals (and then send him off to Jerusalem). According to the code I only see trigger for acquiring this trait i.e birth, hereditary, or if refused bribe. How does it develop ?

Also is there some calculation apart from the triggers that expand a trait ?

Many thanks.

Salute !