In The King's Affection, Inspector Seok-Jo, acting on the orders of Hwi's maternal grandfather,
leads some soldiers to the Magistracy where Physician Jung's friends are being held and kills the guards in order to capture the friends and kill them.
In order to spare Physician Jung his punishment, Hwi brings to light evidence that exculpates him (e.g., that he was not actually lying or overcharging for his medicines). However, she does not mention the actions of the Inspector.
Presumably the authority of the magistrates indirectly derives from that of the king, such that attacking and killing the guards in order to take prisoners away from a magistracy represents a serious offense even for an inspector. This would seem even more relevant since the prisoners were awaiting a judgment that would be pronounced by the king himself, so attempting to execute them before he could give a ruling could be seen as a direct challenge to his authority. It seems that mentioning this would be an easy way to rid herself of a serious threat in the inspector, as well as potentially weakening the authority of her grandfather (who is also a threat).
Why would Hwi not mention this?