I agree with Sennacharib, it has to be an individuals choice. We hear about Living Wills, where a person can state at which point they would like to be "unplugged" or assisted with their suicide (a dirty word). I suppose if it was legalised here, I feel that everyone should be able to make a choice and state it via a living will. Then all pressure is off loved ones, hospital staff and even the courts!
Whether a person would be punished spiritually for it, i don't really know. But if our creator is love and understanding, wouldn't we be forgiven for wishing to end suffering?