How did Klaus Fuchs get caught?

Answer 1

Fuchs in January 1950 confessed that he was a spy. Fuchs told interrogators the KGB acquired an agent in Berkeley, California, who informed the Soviet Union about electromagnetic separation research of uranium-235 in 1942 or earlier. He was prosecuted by Sir Hartley Shawcross and was convicted on 1 March 1950. He was sentenced the next day to fourteen years in prison, the maximum possible for passing military secrets to a friendly nation.

Answer 2

Klaus Fuchs was caught when British intelligence decrypted Soviet communications that revealed his espionage activities. He confessed to passing classified information to the Soviet Union during his interrogation in 1950. Fuchs was ultimately sentenced to 14 years in prison for his actions.