All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The ruling on the permissibility or impermissibility of eating from the meat of an animal slaughtered by a person who does not pray depends on whether he is a Muslim or a non-Muslim.
Indeed, we have already issued Fatwa 89246 clarifying the ruling on animal slaughtered by a person who does not pray, so please refer to it.
The same ruling applies to the meat of the animal slaughtered by a Muslim who practices some types of Shirk (polytheistic acts).
If he does such acts knowingly and deliberately and they are considered as major Shirk, then he goes out of the fold of Islam and it becomes unlawful to eat the meat of an animal slaughtered by him because he is an apostate.
However, if a person commits some acts of Shirk due to not knowing their rulings, and the evidence is not established against him, or that he did so under compulsion, then he is not ruled to be a non-Muslim just by committing such an act. In this case, it is lawful to eat from the meat of an animal slaughtered by him unless he slaughtered it as a sacrifice for other than Allaah [or for idols, or mentioning names other than the Name of Allaah when slaughtering the animal etc...]. In such a case, it is forbidden to eat it.
Allaah Knows best.