Jerry Chun Shing Lee, 55, was sentenced to 19 years in prison on Friday

A former CIA case agent was sentenced to 19 years in prison for an espionage conspiracy in which prosecutors say he received more than $840,000 from China to divulge the names of human sources and his knowledge of spycraft.

The sentence imposed on Jerry Chun Shing Lee, 55, by a federal judge in Alexandria, Virginia on Friday was significantly longer than the 10-years sought by defense attorneys.

Lee pleaded guilty to conspiracy to commit espionage in May, but prosecutors and defense lawyers disagreed about whether there was proof Lee carried out any actual espionage.

Lee´s lawyers disputed that their client´s conduct was anywhere near as severe as the government described.

Prosecutors say Chinese intelligence officers gave Lee more than $840,000 over a three-year period beginning in 2010, and that Lee likely gave them all the information he had from a 13-year career as a CIA case officer. They sought a prison term of more than 20 years.

Lee (pictured right, blue tie, on October 13, 2017 at an unveiling of a painting in Christie's, Hong Kong) was accused of handing the identities of American agents to the Chinese

Defense lawyers say the government never proved that the money came from China or that Lee ever carried out any plans to deliver government secrets.

'What the government is describing is their worst possible nightmare,' said defense lawyer Nina Ginsberg, but she argued that the government could only speculate that its nightmare scenario actually occurred.

Prosecutors acknowledged they had no direct evidence to prove what was transmitted, nor proof that the $840,000 in cash that Lee deposited into his bank account came from Chinese intelligence.

But prosecutors said Lee was never able to come up with a good explanation for where he got the cash. He ran a tobacco business in Hong Kong, but it was essentially a failure, prosecutors said.

'The only logical conclusion,' said prosecutor Neil Hammerstrom, is that that Chinese intelligence 'must have been getting top-drawer, high quality (information) from this defendant.'

Prosecutor Adam Small said the government believes Lee turned over information that was found in a notebook and thumb drive that were found in his possession. That included the names of eight CIA clandestine human sources, Small said, people that Lee himself recruited and handled in his years as a CIA case agent from 1994 to 2007.

Small said the Chinese intelligence officers who met with Lee also gave him more than 20 'taskings' in which they sought details of CIA spycraft, like how they communicate with sources and maintain their cover.

'Everything he knew would have been highly valuable to the PRC,' Small said.

At Friday´s sentencing hearing, U.S. District Judge T.S. Ellis III sided largely with prosecutors. He said he agreed with the conclusion that at least some of the money Lee put into his bank must have come from China, and that he in turn must have divulged at least some classified information.

'I do think something of value changed hands. I just can´t be certain,' Ellis said. At a sentencing hearing, though, Ellis said prosecutors need not prove beyond a reasonable doubt that an act occurred for him to take it into consideration. He can consider it if prosecutors prove it to be more likely true than not.

Ginsberg said there´s no evidence that any of the sources identified in Ginsberg´s notebook were harmed or compromised in any way.

'I dare to say the government would certainly know if their agents had been exposed,' Ginsberg said.

At a press conference after the sentencing, though, U.S. Attorney for the Eastern District of Virginia G. Zachary Terwilliger disputed that assertion. He acknowledged that the U.S. might know if one of its sources suffered physical harm, but could have no idea if the Chinese used that information in a more subtle way.

'We have very talented adversaries,' he said. 'It could be used in a multitude of ways.'

Terwilliger said Lee joins the 'wall of infamous traitors' who have been prosecuted for spying at the Alexandria courthouse, which has jurisdiction over the CIA and large parts of the intelligence community.

In particular, Lee´s case drew comparisons to Kevin Mallory, a former CIA officer who was sentenced to 20 years in prison earlier this year for disclosing secrets to China in exchange for $25,000.

Prosecutors said the money Lee received dwarfed what Mallory got and shows that Lee´s activities were even more severe. Defense lawyers responded that nothing disclosed by Lee exceeded the 'Secret' classification level, while some of what Mallory disclosed was classified as Top Secret.

Lee, for his part, apologized for his actions.

'I take full responsibility for my conduct,' said Lee, a naturalized U.S. citizen who immigrated to Hawaii from Hong Kong with his family when he was 15.