This Reuters article reports:
Dr Philip Nitschke, who says he was the first doctor in the world to administer a legal, voluntary, lethal injection, said it is time for Britain and others to heed growing calls for choice about dying, and allow access to effective suicide drugs.
That claim is echoed in other places, such as this The Guardian article:
Philip Nitschke was the first doctor in the world to legally administer a lethal injection
The event happened in 1996, which sounds pretty late to me. Is Philip Nitschke the first doctor in the world to administer a legal, voluntary, lethal injection?
It sounds surprising to me because I would bet that at least some countries had some loophole or more lenient laws that didn't make euthanasia illegal. E.g. Uruguay:
Since 1932 the Penal Code of Uruguay, article 37, accept Compassionate Homicide, the first legal document that include euthanasia. It's important to say that this legal document didn't use this denomination. In another article, 127, the judge could waive the doctor, if this action was made by patient pledge and the doctor had an honorable reputation.