A Chinese-born engineer initially denied passing military secrets to China with the help of his younger brother, then admitted the allegations several days later, a U.S. Navy investigator testified Tuesday.

Gunnar Newquist, a special agent with the Naval Criminal Investigative Service, played an hour of excerpts from a 4 1/2-hour, secretly videotaped interview done after the arrest of defendant Chi Mak in which he repeatedly denied passing sensitive military information to China.

"I know your suspicion. ... I did not contact anybody, I did not pass things to people purposely," Mak said. "I don't care if you believe or not believe. ... I'm just telling the facts."

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Newquist said Mak made his confession two days later during an untaped interview.

Mak, a naturalized U.S. citizen who worked for a California-based naval defense contractor, has pleaded not guilty to charges of conspiracy to export defense material to China, failure to register as a foreign agent, attempted and actual export of defense articles and making false statements.

His wife, brother and other relatives also have been indicted.

Mak, 66, was arrested on Oct. 28, 2005, after his brother and sister-in-law were stopped at Los Angeles International Airport as they tried to board a flight to Hong Kong and Guangzhou, China.

FBI agents found encrypted disks containing copies of documents on a submarine propulsion system hidden in their luggage, according to court papers.

During cross-examination, Newquist acknowledged that the documents on the discs had been presented by Mak at a 2004 meeting of the American Society of Naval Engineers and distributed to attendees afterward.

He also acknowledged that the documents that Mak was accused of trying to pass to China were not classified until the summer of 2006 — about eight months after his arrest.

In the interview done on the night of his arrest, Mak acknowledges that the documents on the submarine propulsion system were found on the disks but said he gave them to his brother so he could use them to find Chinese-language textbooks for Mak on similar topics, such as electronic power and motor drives.

He also said in the interview that although the propulsion document was marked NOFORN — meaning it could not be shown to foreigners — many non-U.S. citizens attended engineering conferences that included information on the propulsion system.

Mak said he did not consider it a good report and did not think his brother would show it to anyone else.

Newquist testified, however, that during a jail interview two days later, Mak admitted he had been passing information to the Chinese for two decades and had a government contact in Guangzhou, China, named "Mr. Pu."

Mak allegedly told the agent that until 2001 he would take sensitive documents to his brother in Hong Kong, and his brother would pass them to Mr. Pu. His brother moved to the United States in 2001.

Mak said he had passed along military secrets on an electromagnetic aircraft launch system and studies on the survivability of U.S. naval ships, Newquist testified.

Mak allegedly told the agent he was not paid for passing the information, but Mr. Pu took care of his sister-in-law's ailing mother, who lived in Guangzhou, China.

Mak became angry when his Chinese contact began sending him "tasking lists" through his brother, the agent testified.

"Those lists made him mad. When he began passing information, he chose what to give," Newquist said.

Newquist said that during a search of Mak's home, investigators found hundreds of pages of documents marked NOFORN.

Court papers indicate investigators found documents on the DDX Destroyer, an advanced technology warship, and lists in Chinese asking Mak for information about torpedoes, electromagnetic artillery systems and technology used to detect incoming missiles.

Four of Mak's relatives await trial in the case.

His brother, Tai Mak, is charged with conspiracy to export defense articles, possession of property in aid of a foreign government, failure to register as a foreign agent and making false statements.

Chi Mak's wife and Tai Mak's son and wife are all charged with conspiracy to export defense articles, failure to register as a foreign agent and making false statements.