A former East German secret police officer has been sentenced to 10 years in prison for murdering a Polish man attempting to flee to West Berlin 50 years ago.

Martin Naumann, now 80, shot Czeslaw Kukuczka in the back at Friedrichstrasse station in 1974, after he had entered the Polish embassy claiming to be carrying a bomb and demanding to be allowed to leave to democratic West Germany.

Details of the killing remained unknown for decades after the Stasi secret police shredded files relating to the case before communist East Germany reunified with the West in 1991.

Berlin prosecutors filed charges against him in 2023 after persistent investigations by historians and Polish authorities.

On 29 March 1974, 38-year-old Kukuczka, a firefighter, entered the Polish embassy on East Berlin’s Unter den Linden boulevard with a briefcase.

The father of three said – falsely – that he was carrying a bomb. He demanded to be allowed to leave for West Berlin.

Stasi officers gave him an exit visa and some West German money and escorted him to Friedrichstrasse station, which was still served by trains from the western side of the city.

Kukuczka passed several border checks inside the station. However, before he could make it to the West Berlin platform, a man approached him from behind and shot him in the back.

A group of schoolchildren from Hesse in West Germany, were among witnesses to the killing. Some gave evidence at the trial that they had seen a man shoot Kukuczka before “people in uniform” sealed off the passage.

Details of the case were uncovered by historians, who tracked down related files in the Stasi archives. Some documents linking Naumann to the killing, which had been shredded, were reconstituted using a purpose-built machine.

Kukuczka’s family was never officially told of his fate. His ashes were sent to his wife some weeks after his murder.

The case was brought to trial after Poland issued a European arrest warrant for Naumann in 2021.

The trial has been seen as holding special historical significance in Germany, similarly to trials of surviving Holocaust perpetrators.

Naumann always insisted on his innocence. His lawyer has said there was no proof he carried out the killing.

East Germany was created from the parts of Germany occupied by the Soviet Union after the defeat of Nazi Germany in 1945. It was a communist dictatorship, while West Germany – created from the American, British and French occupation zones – was a capitalist, democratic state.

In 1991, both countries reunified to form modern Germany.