A Navy officer who spent time at the Pentagon and served in a secretive squadron pleaded not guilty to espionage charges Tuesday during a hearing at Norfolk Naval Station.

Lt. Cmdr. Edward C. Lin faces two counts of espionage, three counts of attempted espionage and five counts of communicating defense information, The Virginian-Pilot reported. If convicted by a panel of officers of the espionage charge, Lin could face the death penalty. No trial date has been set.

Lin is accused of spying for a foreign power from 2012 to 2014, during which time he was primarily a staff aide to Vice Adm. Joseph Mulloy. It is not publicly known what classified information Lin is alleged to have passed on, but his attorneys have said he’s accused of spying for Taiwan, where he was born. Lin moved to the U.S. when he was 14 and became a citizen in 1998, a year before joining the Navy, The Virginian-Pilot reported.

While in the Navy, Lin worked at the Pentagon and also was part of a squadron in Hawaii, where the military believes some of the information handoffs may have occurred.

The Navy has designated Lin’s prosecution as a “national security case.” He was arrested at the Honolulu airport in September.

Lin’s attorney contended during a preliminary hearing that some of the charges against his client stem from entrapment.