2,528. The Slaughter of a Sadducee

Hilchos Shechita 4:15

If someone is disqualified as a witness for violating a Biblical prohibition, he may still slaughter privately if he's proficient because one wouldn’t ignore something permitted in favor of something prohibited. This presumption applies to all Jews, even to those who are considered evil.

Hilchos Shechita 4:16

The slaughter of the Sadducees and other sects that err by not believing in the oral Torah is prohibited but if they slaughter in front of us, it’s permitted. This is because their slaughter is only prohibited because of the possibility that they might make a mistake; since they don’t believe in the laws of shechita, we do not take their word when they claim not to have erred.