Sperber was thus arrested at home just hours after Stiller defected and immediately confessed. It would have been difficult for him to deny it as the DST most likely knew all that had been going on and thanks to Stiller, the police now had an overwhelming case against Sperber.
The affair caused a stir the moment it was made public: it is not every day that a physicist is accused of spying. The wildest rumours began to circulate immediately, with one journalist even claiming that Sperber sent the East secrets of a French death ray! It was a rather fanciful extrapolation: the atomic physicist, as he was called in the press, had indeed closely studied the actions of powerful lasers to achieve nuclear fusion, but he had not been working to develop a formidable weapon, the so-called ‘death ray'.
It is true though that this spy story had everything to excite the imagination, including that of a prolific thriller writer called Gerard de Villiers, who published an article about Sperber in Paris Match magazine, as well as other general articles on the infiltration of communist spies in France. He even accused a genuine scholar, Jean-Pierre Vigier of having favoured Sperber's entry into the CNRS, under the pretext that he was a communist. Vigier was a renowned physicist, a stalwart of the French university and a resistor, who had broken with the Communist Party a long time ago. He was now a member of the right-wing majority and had to stand before the National Assembly where he was accused of being complicit with Sperber. According to them, the physicist had been researching the neutron bomb and had sent all of its secrets to the East.
The affair, which was taking on an increasing political angle, became more and more important and was to upset the entire French research community. The French scientists were initially stunned. The accusations were serious: their German colleague was suspected of passing intelligence to a foreign power. But little by little their opinions changed, with the attack on Jean-Pierre Vigier being the real trigger and soon Sperber would benefit from a broad sense of solidarity from his colleagues.
After the period following his arrest, Sperber raised his head and began fiercely defending himself. He strongly denied ever belonging to any intelligence service, explaining that he could well have been in contact with secret agents, without being one himself. Yet there were still the methods that he used to pass over information, methods that only a spy could know. Sperber claimed that it was the Cold War climate and the isolation of the GDR that had forced him into it, saying that his fellow East German scientists were not able to travel freely. He therefore came to their aid by sending them documents that they could have easily obtained themselves, had they been able to travel to France. The documents were consequently not secret, but merely papers on theoretical physics.
Sperber counterattacked further by claiming that scientists had the right to communicate with their colleagues around the world: science, he said, was supranational. This still does not explain the spy methods used, but he declared that he was merely trying to prevent a possible breach of secrecy by avoiding the postal service. But if the documents were not secret, then what was there to fear?
Clearly the East German scientist's defence was not entirely convincing. In any case, both he and his supporters did not let it go, pointing out there that was no article of law that prohibiting sending a letter by post written that had been written in invisible ink. Neither was there a ban on listening to the radio! Sperber had been accused of receiving coded messages via radio, messages that had been sent by the East German secret services. Last but not least, however, Sperber loudly proclaimed that he had never harmed the interests of France.
His arguments were credible enough for hundreds of renowned scientists to come to his rescue by signing a petition calling for his immediate release and denouncing the climate of ‘spy mania' that had been generated by the whole affair. Yet Sperber remained in prison and as he continued to deny being a spy, he refused to entertain the idea of a spy exchange between France and the East.
A genuine judicial marathon now began.When Sperber was arrested the State Security Court still existed, before which he had appear. However, the court was removed in 1981 by the Left because it was considered unnecessary and so the physicist was instead to be tried before a military court. Just before its removal the State Security Court had recognised that Sperber had not divulged any national defence secrets.
Sperber avoided facing a military tribunal and was taken instead to the Court of European Justice as he had been held for more than three years without a trial. He was released on bail in 1983 and after many legal challenges, he appeared before the Penal Court in Paris in 1990, eleven years after his original arrest. He was sentenced to twelve years imprisonment, but the outcry from the scientific community was so strong that he was released after six months. The judgement was reconsidered again in late 1991, but this time Sperber was acquitted - after he had spent nearly five years in prison altogether.
Despite the urgings of Sperber's lawyers,
