It’s a risky move, but if the pratfall is grounded in the detective’s habit—say he always bumps his elbow on the evidence board when he’s nervous—it can feel natural. Just make sure the slip doesn’t cheapen the stakes; the suspect still needs to feel the weight of the interrogation. In noir, the humor should serve the tension, not replace it, so keep the timing precise and the character’s motive clear. If you can nail that balance, a little slapstick can humanise the scene without undermining the noir vibe.