Since 2008 almost 60 people in the US have been charged with espionage conspiracies with China or efforts to pass classified information, sensitive technology or trade secrets to the Chinese.
US fears growing threat of domestic spies in pay of China
He had been a seemingly all-American, clean-cut guy: no criminal record; engaged to be married; a job teaching English overseas. In letters to the judge, loved ones described the 29-year-old from Midwest America as honest and caring — a good citizen. His fiancée called him "Mr Patriot".
Such descriptions make the one that culminated in the courtroom all the more baffling: Glenn Shriver was also a spy recruit for China. He took $70,000 from individuals he knew to be Chinese intelligence officers to try to land a job with a US government agency — first the State Department and later the CIA.
Shriver is just one of at least 57 defendants in federal prosecutions since 2008 charged with espionage conspiracies with China or efforts to pass classified information, sensitive technology or trade secrets to intelligence operatives, state-sponsored entities, private individuals or businesses in China.
Of those, nine are awaiting trial and two are considered fugitives. The other defendants have been convicted, though some are yet to be sentenced, according to an Associated Press review of US Justice Department cases.
Most of these prosecutions have received little public attention — especially compared with the headline splash that followed last summer's arrest of 10 Russian "sleeper agents" who had been living in suburban America for more than a decade but, according to Attorney General Eric Holder, passed no secrets.
Contrast that with this snapshot:
• In Honolulu, a former B-2 bomber engineer and one-time professor at Purdue gets 32 years in prison for working with the Chinese to develop a vital part for a cruise missile in a case that a Justice Department official said resulted in the leak of "some of our country's most sensitive weapons-related designs".
• In Boston, a Harvard-educated businessman is sent to prison, along with his ex-wife, for conspiring for a decade to illegally export parts used in military radar and electronic warfare systems to research institutes that manufacture items for the Chinese military. The Department of Defence concluded the illegal exports "represented a serious threat to US national and regional defence security interests".
• In Los Angeles, a man goes to jail for selling Raytheon-manufactured thermal imaging cameras to a buyer in Shanghai whose company develops infrared technology. The cameras are sensitive because of "their potential use in a wide variety of military and civilian applications," according to court documents.
• In Alexandra, Virginia, there is Shriver, who told the judge: "Somewhere along the way, I climbed into bed with the wrong people."
All five of these defendants were sentenced over an 11-day span this year.
In Shriver's case, when once he asked his Chinese handlers — "What, exactly, do you guys want?" — the response, as detailed in court documents, was straightforward.
"If it's possible," they told him, "we want you to get us some secrets or classified information."
Despite denials from Beijing, counter-intelligence experts say the cases reveal the Chinese as among the most active espionage offenders in America today, paying more money and going to greater lengths to glean whatever information they can from the United States.
Just after the New Year, at an airfield in Chengdu, the Chinese military unveiled its first prototype stealth fighter jet: a radar-eluding plane called the J-20, which made its maiden test flight even as the US defence secretary, Robert Gates, was in Beijing on a rare visit.
If most Americans paid little attention, US defence analysts were watching closely. And they were caught a bit off-guard. Mr Gates would later acknowledge that the flight came six months to a year before intelligence estimated it might happen.
So how did the Chinese do it? Was it reverse-engineering from parts taken after an American aircraft shot down over Serbia in 1999, as some Balkan military officials have alleged?
Or was some of the technological know-how obtained through a US engineer who spent several years working illegally to help the Chinese develop stealth technology?
A federal prosecutor raised the possibility of a link between the activities of Noshir Gowadia, once a key engineer on America's B-2 bomber programme, and the faster-than-expected development of Chinese stealth aircraft designs. The comments came just before Gowadia was sentenced to prison in a Honolulu court in January on espionage charges.
Assistant US Attorney Ken Sorenson wrote in a court filing: "China aggressively seeks US defence technologies, and the People's Liberation Army are now shown to have been actively working on stealth aircraft designs, most certainly during Gowadia's visits there," noting Gowadia worked in and with China for two years developing a stealth engine nozzle design.
For years, US counter-intelligence experts have cited a growing espionage threat from China.
Recent cases reveal not only a high level of activity but also signs of changing tactics and emboldened efforts. In one case, a convicted spy managed to convince not one but two US government officials to pass him secret information, telling them it was going to Taiwan when he instead passed it to a Chinese official.
The recruitment of more non-Chinese, such as Shriver and Gowadia (an India-born, naturalised US citizen), also represents a shift, said Larry Wortzel, a former Army intelligence officer who serves on the US-China Economic and Security Review Commission. In the past, said Mr Wortzel, China preferred to deal with those "assessed as sympathetic to China or with ethnic Chinese."
And then there are the so-called "espionage entrepreneurs," motivated simply by money.
When asked about the recent cases, the Chinese Foreign Ministry questioned the statistics, responding in a faxed statement: "To speak of the Chinese side's so-called 'espionage activities' in the United States is pure nonsense with ulterior motives."
However, Joel Brenner, who served as the US National Counter-intelligence Executive from 2006 to 2009, said: "The Chinese espionage threat has been relentless recently. We've never seen anything like it. Some of it's public. Some of it's private. And some of it lies in that ambiguous area in between."
Today's "agents" are professors and engineers, businessmen exporting legitimate products while also shipping restricted technology and munitions, criminal capitalists who see only dollar signs. While some may be acting at the direction of a government handler, others supply information to firms for either private enterprise or state-sponsored research — or both.
Driving all of this, US officials said, is China's desire to develop a modernised military and its burgeoning wealth; last year China surpassed Japan as the world's second-largest economy, now behind only the United States.