Worked in a slaughterhouse in the 70s, doing some building work. The Asian bloke came round about once a week, said a few prayers while he slit the throat of a few sheep over the cradle, once he went, the men carried on doing the same thing without praying. The only time i saw the imune way of killing a sheep was when the inspector came round, like using an electric stunner. But my point is, all the carcasses got stacked together in a big freezer, and when asking the owner which are the halal sheep, he replied " Ive not a fucking clue".