I recently read Stranger's Handbook (need a translator) and when a noble try to enslave some adventurers he lie. But after the woman adventurer tell the truth somehow he don't know how to lie anymore and is killed. A BIG WTF ! If he kept lying he had a small chance to survive / capture them. But before that i thought, WHAT IF when assassins /or/ bandits are captured and tortured (to tell their sender) why can't they lie and tell the name of a good guy / ennemy of the sender ? Or they can tell a random name that the sender gave. So with what i said, don't you think it's bad that often in isekai there is no lie detector ? People can just accuse anyone with whatever they want and can just bribe lot of people or important ones to join them. Ex: the noble in I was a sword could lie / accuse easily with his skill. He had also a lie detector but it's rare for the populace. PS: The only isekai i saw that had a lie detector was The lazy dungeon master.
I’m a NEET but When I Went to Hello Work I Got Taken to Another World have truth inspector which can see through lie. konosuba also have one.
Boundary labrynth and foreign magician has lie detector magic as a guarded national skill. The author did put some thoughts into the world building as there is slavery magic as well as political twisting which makes it important to keep those who know the skill from being exposed to those threats.
Imo it's fking stupid, but hey their existence is stupid to begin with. Best way of getting the truth is to painfully torture someone mentally and break all his/her barriers making 'em see a light of survival before erasing that as well in the end. Reason why I like Forty millenniums of cultivation ( ones that read up to date will understand)