And if the one who stoned is not stoned, etc. - ומה הסוקל אינו נסקל
Summary:
According to רש"י the ק"ו of ומה הסוקל is the same as הרגו אינן נהרגים. According to תוספות the ק"ו is from a person who actually stoned someone to death, but nevertheless he receives הרג (not סקילה) so the עדים who merely want to punish the accused with סקילה should certainly not receive סקילה.
