A Navy officer facing espionage charges for allegedly handing military secrets to Taiwan and China was entrapped in a "nefarious scheme" by government agents, his lawyer argued in testimony made public Thursday.

Prosecutors say Lieutenant Commander Edward Lin -- a decorated Navy veteran -- committed a string of offenses including espionage, mishandling classified information and failing to follow lawful orders. He is also accused of adultery and using a prostitute.

Given the sensitive nature of the case, much of it remains classified, but the Pentagon on Thursday played reporters a recording of parts of Lin's initial hearing last month.

"The defense maintains that the government has engaged in a nefarious scheme to entrap Lieutenant Commander Lin," defense lawyer Larry Youngner said during the so-called Article 32 hearing, which took place April 8 at Naval Station Norfolk, Virginia.

Without going into details, Youngner said his client had been "enticed" by a Mandarin-speaking FBI informant during a series of meetings beginning last August.

"Did the government prey on his vulnerabilities and entice him to engage in something he would not otherwise have engaged in?" Youngner asked.

Prior to his arrest, Lin, 39, was assigned to a special squadron based out of a Marine Corps air base in Hawaii that flew special intelligence-gathering planes.

Youngner also questioned whether the information Lin had carried was actually classified, or whether it was all "open source."

Prosecutors said their evidence comes partly from two days of interrogations after Lin's arrest at Honolulu airport on September 11, 2015, and that Lin had admitted to a string of specifications outlined in the charges against him.

Youngner responded by saying the interrogation and subsequent evidence were tainted because Lin had not been properly read his rights.

Lin's defense team also said the government had tried to sensationalize the case by adding the prostitution and adultery charges, saying those allegations should be dealt with separately.

The officer who headed Lin's hearing has made a recommendation to the commanding admiral about whether the case should be referred to a full court-martial, but no decision has been made public.

Lin remains in custody at the naval brig in Chesapeake, Virginia.

The case emerges amid heightened tensions between China and regional neighbors in the South China Sea, where Beijing is building massive military structures including radar systems and an airstrip over reefs and tiny islands in contested waters.

A 2008 Navy article says Lin left his birthplace of Taiwan when he was 14 and eventually became a naturalized US citizen.

Although the Navy has said Lin passed secrets to China, Taiwan and possibly other countries too, only Taiwan was referenced in the 80 or so minutes of testimony made available Thursday.

Youngner did not immediately return a call seeking additional comment.