In "Looting The Louvre", "Sneaking & Entering", or "To The Manor Borne", while you are running and not about to hide behind a statue (for example, at the end of "Lootivg The Louvre", there are a few seconds when you are just running and not actually doing anything), select any of the "statues" things on the touch screen. If done correctly, Raphael should "trip".