The investigation implicated officials in the government of then-prime minister, now President Tayyip Erdogan
A Turkish prosecutor said on Tuesday a US consulate employee should be acquitted on charges of espionage and trying to overthrow the government, but should face jail on a lesser charge of belonging to a terrorist organization.
The prosecutor told an Istanbul court that the evidence did not back up the original charges against Metin Topuz, who has been in jail for nearly 2-1/2 years while facing trial.
Topuz's trial has been one of many sources of strain between NATO allies Turkey and the United States, who have also been at odds in recent years over policy differences in Syria and Turkey's purchase of Russian missile defense systems.
In a 78-page indictment that includes telephone calls, text messages and CCTV images, Topuz is accused of links to officials who led a 2013 corruption investigation and were later found to be members of a network blamed for a failed 2016 military coup.
The investigation implicated officials in the government of then-prime minister, now President Tayyip Erdogan.
The prosecutor said the frequent contact Topuz had with members of Fethullah Gulen's network taking part in the investigation showed he was a member of the group, which is considered a terrorist organization by Ankara.
He requested that Topuz be sentenced to up to 15 years in prison, compared to a life sentence that he could have received if found guilty on the original charges.
The court rejected a request by defense lawyers for Topuz's release and postponed the trial until June 11, according to one of the defense lawyers.
A translator and fixer for the US Drug Enforcement Agency (DEA) at the US consulate in Istanbul, Topuz has maintained throughout the trial that he contacted the individuals, who at the time held high-ranking positions in the police and judiciary, as part of his job.
Gulen has lived in self-imposed exile in the US state of Pennsylvania since 1999, and has denied any involvement in the coup attempt.