I'm a frequent enough patron of the halal food truck near where I work that they recognize me and know my order (falafel). I don't eat the meat, but I find myself wondering about it as an intellectual question. I don't have enough information to answer the question, and even if I were to answer it in the affirmative, I'm not sure I would actually act on it -- as a flexitarian meat-reductionist, I don't feel like I need to give myself more opportunities to eat meat. But it's still an interesting question to ponder.
As I understand it, kosher meat and halal meat both must be slaughtered by a particular process and the processes are similar, and both must have the blood removed. So the question is: can someone who keeps kosher eat halal meat (from a kosher species)?
The most obvious answer is "No, of course not!" This is because kosher meat must be slaughtered by a Jew, a requirement that is obviously not met by halal meat. But what if we weren't concerned about this particular requirement? This change might be motivated by a sense of inclusion: Muslims are "people of the book" (as it were), and their slaughter is also performed in the name of the One God, and not idolatry. Or it might be motivated by the opposite sentiment: outside of Hazon conferences, liberal Jewish communities generally don't do their own slaughter, and so the Jews who slaughter the meat that we eat are far outside our communities, and are so alien that it wouldn't make much of a difference if they were Muslim. Or some linear combination of both reasons. So if this requirement were to be lifted, would it be ok to eat halal meat?
For beef or lamb, the answer is still no. In mammals, the gid hanasheh (sciatic nerve) and cheilev (the fats that would have been offered on the altar) are not kosher and must be removed. (This is done by the butcher before selling the meat.) Halal meat has no such rules, and therefore must be under the presumption of containing these forbidden parts. Most of us casual meat-eaters can't look at meat and identify what part of the animal it comes from (especially when it's in shwarma form).
But what about halal chicken? Gid hanasheh and cheilev don't apply to birds, and my recollection is that the regulations for slaughtering birds are less strict than for mammals. So the question is whether the procedure for slaughtering halal birds would qualify under the rules of slaughtering kosher birds, and likewise for the procedures for removing blood from halal/kosher meat. I can't answer these questions; I haven't studied shechitah in any depth (beyond the Mishnah, and that was a long time ago), and don't know the specifics of halal slaughter. (And if I'm going to study any masechet in the next few months, it's going to be Kiddushin.) So can anyone with more knowledge on the subject weigh in on this question?