Lethal Injection involves injecting someone with fatal doses of poisonous drugs to cause death. It is the main form of execution currently used in the United Stated of America. In fact, every execution in the USA in 2005 was by lethal injection. This form of capital punishment became common in the twentieth century, because other forms of execution were considered less humane. However, the humaneness of lethal injection is also questioned.
Nazi Germany's T-4 Euthanasia Program used lethal injection (with drugs that differed from the modern method) as one of several methods to destroy "life unworthy of life."
Apart from the United States of America, China, Guatemala, and the Philippines have used lethal injection. Other countries have also adopted it legally, but have not used it.