Honest Adviser: The non-sophont AIs built to advise various runér, Senators, etc., are programmed to be this. And provably so! With code reviews!
You can do this with sophonts, too, digital or biological, these days – given the ability of geas nanotech, alethiometers, and the ability to muck about with the loyalty circuits in people’s heads. This, on the other hand, is by no means the general practice. The Empire greatly prefers to cultivate a culture of straight talking and honest dealing than to demand that people submit to alethiometric verification or geatic enforcement for every little thing. (Although it’s nice that the option is there when dealing with people whose words have less value, belike.)
And, of course, constitutionals of the Transcend can trust each other thus as a matter of course.