The only "mercy" they deserved was for a long drop instead of the short one from the back of trucks.
In the old hanging days at the Tyburn gallows, family and friends would hang onto the dying persons legs to try and hasten the strangling death. It's a drawn out death of suffocation that usually lasted up to 10-15 mins. Brutal.
With The long drop, a little bit of math is required. The knot goes just behind the left ear so that when the bottom drops out, the weight of the body snaps the neck. But too long a drop and heads be popping off.