Assalam o Alaikum, While slaughtering if the head of the animal get completely apart by mistake and not deliberately, can we consider it as halal? JazakAllahu Khairan

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, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.

Cutting off the head while slaughtering is not prohibited and it does not render the slaughtered animal prohibited to eat. However, some scholars considered it Makrooh (disliked) to detach the head during the slaughtering before the animal is completely dead because it involves torturing the animal. But even if it is done, the slaughtered animal is still Halaal. Ibn Qudaamah wrote,

“It is not permissible to cut off any part of the slaughtered animal before it is completely dead. The scholars considered that disliked, among them ʻAtaa’, ʻAmr ibn Dinaar, Maalik, Ash-Shaafi‘i, and we do not know of anyone opposing them. ʻUmar said, "Do not rush the life before it leaves the body."

The strongest scholarly view in this regard is that it is not prohibited to remove or cut off any body part of the slaughtered animal during the slaughtering before it is completely dead. It has been reported that Imaam Ahmad was asked about a man who slaughtered a hen and cut its head off (before it was completely dead). He replied, "It is lawful to eat its flesh." It was further asked, "Even the part that was cut off?" He said, "Yes."

Al-Bukhari said that Ibn ‘Abbaas and Ibn ʻUmar were of the opinion that if its head was severed and separated from the body during the act of slaughtering an animal, there is no harm (and the meat of the slaughtered animal is lawful for consumption). This view was adopted by ʻAtaa’, Al-Hasan, An-Nakha‘i, Ash-Shaʻbi, Az-Zuhri, Ash-Shaafiʻi, Is-haaq, Abu Thawr and the Hanafis, because cutting off that part of the animal after slaughtering it is (effectively) like cutting it off after the animal’s death.” [Al-Mughni]

Allaah Knows best.