Are false witnesses who are trying to give you the death penalty considered rodfim that you would be allowed to kill? (if you have no other way of stopping them) obviously it would have to be done in secret b/c other people would consider you a rodef and be allowed to kill you or at least testify in beis din and beis din would kill you.
binayahu chayim, USA
The Minchas Chinuch (Mitzva 600) writes, "And all other cases where the murderer is not given the death penalty such as where he ties the victim in front of a lion, etc. perhaps since the Rotzei'ach cannot be given the death penalty then he cannot be killed as a Rodef."
The Machon Yerushalayim edition of the Minchas Chinuch note 1 brings the Rivash's opinion which applies Rodef even to Gerama death and also brings the Rashba that seemingly argues.
But the Achiezer 1:19:3-4 refers specifically to your case and says that witnesses cannot be called Rodfim at all since their testifying is not an act clearly identified to all as an attempt to kill, and killing them is forbidden.
All the best,