The woman, who has not been named, heard in court on Wednesday that she was not guilty of manslaughter and would not be going to prison. Instead she would receive an eight month suspended sentence for denial of medical assistance to the fatally wounded 18-year-old and for breaching the country's weapons law.
The man entered the shop in Wetterau, Hesse, in July 2011 wearing a mask. He held an unloaded air gun and demanded money.
The woman went into a back room, where she had a hidden revolver, and shot him from a distance. The bullet hit the teen in the back of the head.
Prosecutors said they saw no case for self-defence, arguing that if it had been, she would have fired a warning shot or shot him in the leg.
But the judge at the Gießen regional court in Hesse said she could not have known that his gun was not loaded and that the woman was clearly affected by the incident.
“I was holding the weapon in my hand and suddenly it fired,” she told the judge, an incident that her defence called “purely accidental.” The court gave her a suspended sentence for failing to alert the emergency services quickly enough, and instead ringing her husband.
Initially the woman told the police that the robber's accomplice had shot him, which was found to be a lie.