Dear Baltimore,
Maybe the reverse can be deduced from this gemara. Since even in this instance the gemara (To my memory.) included the witnesses, it seems that the entire death penalty may actually hinge on the witnesses personally carrying out the execution. Maybe it follows that the witnesses cannot be forced to carryit out, because then they are on longer witnesses. A forced husband is still her husband. But coerced witnesses makes for for zero testimony. The best resolution I see, is for the convict to remain in the realm of ‘the walking dead’. And the witnesses are required to do teshuva for perverting justice. But they face no direct consequence.