The letter from lawyers for Halkbank executive Mehmet Hakan Atilla was publically filed but was later deleted from the public record.
In it, the lawyers said that prosecutors over the weekend had turned over to them a summary of five jailhouse audio recordings of Reza Zarrab, a Turkish-Iranian gold trader who pleaded guilty in late October in a cooperation deal with the U.S. government.
Zarrab testified for a fourth day Monday that he paid bribes in a conspiracy to help Iran move $1 billion of oil and gas revenues through world financial markets, including U.S. banks, despite sanctions meant to prevent the financial transfers.
Defense lawyers said prosecutors had violated the trial judge's order that any trial exhibits that might help the defense be turned over to Atilla's team immediately. To make their case, they cited several passages in a two-page English summary of audio recordings made in a foreign language.
In a September 2016 recording, Zarrab is quoted as saying that there was a perceived need when incarcerated in the United States to lie "in order to get out or to get a reduced sentence" and that "you need to admit to crimes you haven't committed" to get out of prison, the lawyers said.
"Zarrab is proclaiming his willingness to fabricate testimony out of whole cloth in order to obtain a reduced sentence," the lawyers wrote.
They said the delay in turning over the evidence to Atilla's team "significantly impairs the ability of the defense to properly and effectively utilize them at trial."
Nicholas Biase, a spokesman for prosecutors, declined to comment.
The criminal case has strained relations between the U.S. and Turkey. Turkish President Recep Tayyip Erdogan has repeatedly demanded Zarrab's release and Turkish Deputy Prime Minister Bekir Bozdag has called Zarrab a "hostage" being forced to testify against Turkey.
Bribes paid for release in Turkey
The defense submission came on a day when Zarrab testified that bribes were paid to help secure his release from a Turkish prison after he was arrested in 2013 as part of a sweeping corruption investigation involving the state bank, Halkbank, and several top Erdogan lieutenants.
As Zarrab testified about payments made to secure his release, a prosecutor asked him if the payments were bribes.
"Partly," Zarrab responded.
Zarrab, 34, of Istanbul, has been in custody since his March 2016 arrest as he arrived with his family in Florida for vacation. He is a well-known personality in Turkey partly because he's married to Turkish pop star and TV personality Ebru Gundes.
Earlier this year, Zarrab hired former New York City Mayor Rudolph Giuliani and former U.S. Attorney General Michael Mukasey to try and broker a diplomatic solution to the case.
The summary of jailhouse conversations attached to the defense letter showed that Zarrab was being told by visitors that diplomatic efforts might win his release.
In an October 2016 summary, there was talk that "six people will be exchanged for four people," according to the exhibit.
In the summary of a November 2016 conversation, there was mention that someone working on Zarrab's behalf would try to call then-President Barack Obama if necessary.