Ethically, I think pretty much every code of ethics for doctors suggests that they should not be in an interrogation room, particularly if there's anything coercive or abusive going on. ↗
I have my ethics and morals. I have my anchor point of what is right and wrong in real life, but I'm not afraid to entertain any and every aspect of personality in relationship to creating a character. ↗
If you deny that any principles of conduct at all are common to and admitted by all men who try to behave reasonably - well, I don't see how you can have any ethics or any ethical background for law. ↗