We expect deer to react to the shot (we’ve seen this over and over). We practice like we hunt. When shooting at a deer or target, we aim at the lower 1/3 of the kill zone. If the deer reacts/drops, the shot is still in the kill zone. If the deer doesn’t react, it’s in the heart and/or bottom lungs.
I aim at the bottom third of the deer’s chest whether they are 20 or 40 yards away. I rarely shoot at deer past 40 yards for fear the deer will move and I rarely worry about deer dropping below the flight of the arrow if they are much closer than 20 yards. There are multiple advantages to aiming at the lower third of a deer’s chest. Wounds here usually produce better blood trails because the chest cavity doesn’t have to fill with blood before it starts exiting the wound.
I practice aiming at the bottom third so it’s a normal sight pattern when I’m hunting! See this video that shows how aiming for the lower third pays off!