No. The support hand index finger should not be on the trigger guard. It is a proven fact that as pressure is applied to the trigger in many cases unconscious, sympathetic pressure is also applied to the trigger guard. For right handed shooters this can cause the gun to move slightly to the left asthe trigger is pressed. Now at 3 yrds. or so the off center impact is negligible. But as the shooter moves back 7, 10, 15 yards from the target, bullet impact can move 10 inches or more off center. Plus all fingers not involved in pressing the trigger should be considered gripping fingers and as such should be wrapped around the grip locking the gun firmly in the shooters hands. I always tell shooters, 'Fingers to knuckles, thumb over thumb.'