I'd make a distinction euthanasia and assisted suicide. The later is what you want to allow, and if you want to kill yourself that's OK by me. If you want help in your clearly expressed desire to die, that's OK too, so long as the medical pression isn't forced to help you.
But Euthanasia occurs precisely when the victim has not clearly expressed a desire to die, but someone want to kill them anyway. It's a form of homocide.
So, a depressed 17 year old comes up to you and expresses a desire to die. You'd help him. Right?
The standard has to be that you can be a Killer or a Doctor, but not both!
We might apply that to judges and lawyers as well.