Only a handful of U.S. states have formally legalized assisted suicide, but for decades bioethicists have been concerned about what might be called "stealth euthanasia," when a medical provider effectively brings about the death of the patient under their care by simply ending treatment or by stipulating doses of opiates at levels that kill them. It can be difficult to know when such euthanasia has taken place. As long as one is not aiming at the death of one's patient, there are legitimate circumstances when a physician may make either choice.