2,521. An Untrained Butcher

Hilchos Shechita 4:1

If a Jew who doesn’t know the five things that invalidate shechita and the other laws that we have discussed slaughters an animal in private, neither he nor others may eat that animal; it’s a quasi-neveila out of doubt. If one eats an olive-sized piece of its flesh, he incurs stripes for acting rebelliously.

Hilchos Shechita 4:2

Even if the aforementioned person slaughtered animals correctly in front of people four or five times and the shechita that he performed privately seems wholly correct, it’s still prohibited to eat it. Since he doesn’t know the things that invalidate shechita, it’s possible that he invalidated the slaughter and doesn’t know it. For example, one might unconsciously delay, apply pressure, slaughter with an imperfect knife, etc.