Is mercy killing legal?

Our 80 year old mother has been bed ridden for the past 6 months after suffering a head injury after a motor accident. Apart from being incoherent, she also bed-wets and soils the bed with faeces. Since the doctors have given up on her and we don’t want her to suffer, can we arrange for her to be allowed to pass away quietly through a lethal injection?
Mofe (by SMS)

Euthanasia, also called mercy killing, is the act or practice of painlessly putting to death persons suffering from painful and incurable disease or incapacitating physical disorder or allowing them to die by withholding treatment or withdrawing artificial life-support measures. Because there is no specific provision for it in most legal systems, it is usually regarded as either suicide (if performed by the patient himself) or murder (if performed by another). Physicians may, however, lawfully decide not to prolong life in cases of extreme suffering, and they may administer drugs to relieve pain even if this shortens the patient’s life. The first countries to legalize euthanasia were the Netherlands in 2001 and Belgium in 2002. In 1997 Oregon became the first state in the United States to decriminalise physician-assisted suicide; opponents of the controversial law, however, attempted to have it overturned. In 2009 the Supreme Court of South Korea recognised a “right to die with dignity” in its decision to approve a request by the family of a brain-dead woman that she be removed from life-support systems. However, as of today, Mercy Killing is illegal in Nigeria and should not be practised.