ZURICH, Dec 9 (Reuters) - Switzerland"s supreme court has overturned the conviction of a Geneva doctor who helped a healthy 86-year-old woman commit suicide so she would not have to outlive her dying husband. In the ruling released on Thursday, the Federal Court said a lower court erred in sentencing the doctor under the Therapeutic Products Act (TPA), which it said did not apply. It sent the case back to see if he should be retried under the Narcotics Act. The unidentified doctor prescribed the lethal drug sodium pentobarbital for the woman in 2017, who took it to die along with her spouse, the court said in a statement. In cases of suicide by a healthy person, there is no medical indication for the prescription of sodium pentobarbital, which is not used therapeutically in the broadest sense, so a conviction on the basis of the TPA was invalid, the court said. Assisted suicide has been legal in Switzerland since the 1940s, a legal curiosity that has made the country what some call a "death tourism" magnet.