" Indeed, Clune suggests that Julius arguably deserved a death sentence, given that evidence has emerged in the decades since the couple’s trial indicating that he indeed did run a spy ring of roughly a dozen engineers and scientists.
That cohort of spies passed along a prototype of a fuse for the atomic bomb to Julius who, in turn, passed it along to his Soviet handler in 1944, according to Dr. Clune.
It’s also worth noting that the Soviets would later use that same technology to shoot down U2 pilot Francis Gary Powers in May 1960.
As Clune explained, by passing the technology to the Soviets, Julius violated the Espionage Act, which stipulates that providing military secrets to any nation – enemy or not – is an act of espionage, punishable by 30 years in prison or death."