Assisted suicide is legal in the states of Oregon (via the Oregon Death with Dignity Act), Washington (by Washington Initiative 1000), and Montana (through a trial court ruling). In these three states, subject to substantial hurdles, people are allowed to kill themselves with drugs prescribed by a doctor for such purpose. For example, under Oregon's voter-approved Death with Dignity Act, a terminally ill patient may obtain the lethal drugs if two doctors agree that the person has less than six months to live and is mentally competent to decide whether to end his life.
The majority of states, over 40, have laws making it a statutory crime to assist or aid suicide, e.g., TPC Section 22.08 (Aiding Suicide), or rely on the common law crime. (1)(2)
In fact, physicians have been knowingly (aware that their acts are reasonably certain to cause death) hastening the deaths of their patients since antiquity. They do it many times every day in the USA with "P.R.N." orders. P.R.N. means pro re nata (administer as needed or as the situation arises). When coupled with a morphine drip, the result of a P.R.N. order by a doctor is death by overdose of morphine. There is no accurate frequency data, but this could be accumulated easily by doing drug screens on people who die in hospitals. I suggest to you that perhaps 60% of the geriatric deaths would display lethal doses of drugs, principally morphine, that are given in IV drips to "alleviate pain" under a P.R.N. order. Analytically, these are murders under the common law, Model Penal Code, and law of Texas because they are done knowingly, though not necessarily with intent to kill. See Section 19.02 (b) (1) TPC . There is also a significant amount of low visibility (bootleg) euthanasia in connection with full-blown terminally ill AIDS patients en extremis. (1-Final Exit), (2-pdf article), (3)
For insight, watch online the Frontline Special The Suicide Tourist, the story of Craig Ewert.