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The trial of a Chinese-born American citizen accused of stealing secrets from a cellphone company knowing they would likely end up in the hands of China's military began Monday in Chicago — in yet another case highlighting persistent fears about Chinese espionage.

A prosecutor described Hanjuan Jin as a University of Notre Dame graduate who rose through Motorola Inc. to become a senior software engineer only to violate its trust by stealing documents on confidential technology and trying to flee on a one-way ticket to China.

"This is a woman who led a double life," government attorney Christopher Stetler said in his opening statement.

Jin, 41, did violate policy by removing the documents in 2007 and "Motorola has a right to be upset," defense attorney Beth Gaus conceded in her opening. But she insisted Jin compiled the documents merely to refresh her own technical knowledge after a long medical absence.

What's more, Gaus added, the supposedly sophisticated technology at the center of the trial — a walkie-talkie type feature on Motorola cellphones — was far from cutting edge and would have been little use to China's military.

"It was at a developmental dead end," Gaus said, adding that meant the documents don't meet the legal definition of trade secrets.

Beijing has consistently denied engaging in such activities, though U.S. counterintelligence experts have said signs point to the Chinese as among the most active espionage offenders in the United States.

Jin waived her right to a jury trial, leaving it to U.S. District Judge Ruben Castillo to eventually decide a verdict. Dressed in a dark business suit, Jin looked on during the openings with little apparent emotion — her hands folded on the defense table in front of her.

Jin was about to board her plane bound at O'Hare International Airport in Chicago on Feb. 28, 2007, when a custom's agent stopped her for a random check, then discovering the documents — many stored electronically. She also carried $31,000 in cash.

While on medical leave, prosecutors say Jin began working for a technology company in China unbeknownst to Motorola; when she returned to her Motorola office on Feb. 26, 2007, she allegedly spent two days downloading documents.

The case could be decided on the issue of whether the documents were, in fact, as vital as the government contends.

Another indication that they were not was that Motorola did not take the kinds of precautions to ensure they didn't slip so easily into the wrong hands, Gaus said.

"(Motorola) is asking this court to provide protection of its documents that it did not provide itself," she said.

The government attorney, however, said Motorola had imposed strict security measures, including by setting computer passwords to strict limit access to documents.