I've just been "Demoted" to Arson. Brilliant game but i've found some niggles with the interrogation system too.
I just interviewed a guy and he told me a blatant lie, so i called him on it and presented the evidence and i was correct. But he was staring at me with stone cold dead eyes, indicating he was telling the truth, i only took the gamble because of the evidence. Some interrogations are trickier than others. The "inconsistency" with the interrogation system can be annoying, but i think it adds to the realism and makes you think about it a lot more.