cofty,
My initial reaction to reading Leviticus 11:39,40 (with the background knowledge that I have that blood was forbidden to them as food) was that this was probably written to exclude eating any part of the animal, even if there was no blood involved, as that would be unclean.
I did a bit of research as I was not entirely happy with this explanation and found that John Wesley , in his Explanatory Notes on the Whole Bible, commented on verse 40 and said
40. He that eateth - Unwittingly, for if he did it knowingly, it was a presumptuous sin against an express law, Deut. xiv. 21, and therefore punished with cutting off.
I also found that the Jewish commentators agreed with this.
Maimonides says, in the Mishneh Torah (Hilchot Ma'achalot Assurot 6:1) :
One who eats an olive's worth of blood intentionally is cut off from his people. One who eats it accidentally brings a sin-offering.
Rashi uses this measurement and explains 11:40 as meaning
"Why does the Torah say 'one who eats'? To set a minimum measure for one who carries and one who touches, being a size of an olive."
This seems to me a more likely meaning of the verse, that if you eat such an animal not knowing its origin and then discovered its origin you must be considered unclean until the evening. I think Witnesses take a similar view to eating meat that you subsequently find had not been bled.
I remember an incident when I was pioneering in a rural area some years ago and a buck sprang out in front of our car and we hit it. My partner stopped the car, sprang out and cut the poor animals neck and I had the unenviable task of holding it out the window while the blood drained as we drove home. Needless to say that was the end of field service that day.
I think I should add that while I did describe myself as one of Jehovah's witnesses, the use of a lower case 'w' was deliberate as I am part of the old school who do not view myself as part of a religion but simply consider it a matter of faith. So while djeggnog seems to speak of and for the religion I am not claiming the same for myself.