The filing gives the government the right to file the charges again if it chooses. A spokesman for John P. Carlin, the assistant attorney general who is overseeing the crackdown on economic espionage, had no comment on whether Justice Department officials in Washington reviewed the case.

The science involved in Dr. Xi’s case is, by any measure, complicated. It involves the process of coating one substance with a very thin film of another. Dr. Xi’s lawyer, Peter Zeidenberg, said that despite the complexity, it appeared that the government never consulted with experts before taking the case to a grand jury. As a result, prosecutors misconstrued the evidence, he said.

Mr. Zeidenberg, a lawyer for the firm Arent Fox, represented both Dr. Xi and Sherry Chen, a government hydrologist who was charged and later cleared in the Ohio case. A longtime federal prosecutor, Mr. Zeidenberg said he understood that agents felt intense pressure to crack down on Chinese espionage, but the authorities in these cases appeared to have been too quick to assume that their suspicions were justified.

In Dr. Xi’s case, Mr. Zeidenberg said, the authorities saw emails to scientists in China and assumed the worst. But he said the emails represented the kind of international academic collaboration that governments and universities encourage. The technology discussed was not sensitive or restricted, he said.

“If he was Canadian-American or French-American, or he was from the U.K., would this have ever even got on the government’s radar? I don’t think so,” Mr. Zeidenberg said.

The Justice Department sees a pernicious threat of economic espionage from China, and experts say the government in Beijing has an official policy encouraging the theft of trade secrets. Prosecutors have charged Chinese workers in the United States with stealing Boeing aircraft information, specialty seeds and even the pigment used to whiten Oreo cookie cream.