Reply To: What if the Witnesses Don’t Want to Kill Him?

N0mesorah
It was an intriguing question. Gave me something to do over shabbos.
But to answer your question, I have no clue. The whole thing is an educated guess. But it can’t be hard to get two big guys to grab the arm of the individual and force him to pick up a sword.
The Rambam phrases carrying out the missa as a mitzvas bais din, but we have the limiting factor that the witness has to go first. So my guess is, since it seems to be a necessary component, they force him somehow.