California Republican Rep Darrel Issa believes Special Counsel Robert Mueller's case against Michael Flynn will soon be thrown out of court.

Issa, who is retiring at the end of the year, told Fox News on Sunday that he believed the FBI had 'tricked' Trump's former National Security Adviser into not having a lawyer during a January 2017 interview.

Flynn later admitted he lied to federal authorities investigating possible Russian interference in the 2016 election during the conversation.

Issa made the claims a day before former FBI director James Comey is set to testify again before House Republicans.

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California Republican Rep Darrel Issa believes Special Counsel Robert Mueller's case against Michael Flynn will soon be thrown out of court

Judge Emmet Sullivan ordered both lawyers for special counsel Robert Mueller (right) and former national security adviser Michael Flynn (left) to submit their documents on Flynn's interview in January 2017 at which he has admitted lying to agents investigating possible Russian interference in Donald Trump's election

Comey is being questioned by the committee regarding decisions the FBI made in 2016, including whether there was collusion between Russia and Donald Trump's presidential campaign during the presidential election.

'Tomorrow is going to be a very different day for Comey, particularly in light of what we've learned - the misconduct during the Flynn investigation was all about, thanks to a judge that demanded to understand what happened,' Issa said.

This week US District Judge Emmet Sullivan ordered both the Mueller investigation and Flynn's team to turn over all documents relating to the fateful 2017 interview.

Flynn alleged in a court filling on Tuesday that the FBI pushed him toward having no lawyer present for his January 2017 interview.

His attorneys pointed the finger at then-FBI Deputy Director Andrew McCabe - claiming he pushed Flynn not to have an attorney present for the questioning.

United States District Court Judge Emmet Sullivan demanded all sides turn over their documents relating to the interview

They claimed the FBI threatened to take the matter to the Justice Department if Flynn were to seek counsel before sitting down with its agents.

'I explained that I thought the quickest way to get this done was to have a conversation between [Flynn] and the agents only,' McCabe wrote in a memorandum reported by Fox News.

'I further stated that if LTG Flynn wished to include anyone else in the meeting, like the White House Counsel for instance, that I would need to involve the Department of Justice. [General Flynn] stated that this would not be necessary and agreed to meet with the agents without any additional participants.'

The FBI was not obliged to make clear to Flynn that he had the right of attorney, because he was not in custody.

But Issa believes the cards are stacked in Flynn's favor.

'I would not be surprised a bit if the conviction of Flynn is overturned because of the Justice Department FBI's misconduct,' he said.

'When the FBI and the Department of Justice lies to someone and tricks them into making statements, and then charges them with a lie they entrapped them.'

'This is conduct that we haven't seen in a long time.'

Meanwhile, Mueller has argued that Flynn, a veteran US official, 'does not need to be warned it is a crime to lie to federal agents, to know the importance of telling them the truth'.

The special counsel said that Flynn was 'undoubtedly aware, in light of his "many years" working with the FBI, that lying to the FBI carries serious consequences'.

'Nothing about the way the interview was arranged or conducted caused the defendant to make false statements to the FBI,' Mueller's Friday court filing stated.

'The seriousness of the defendant's offense cannot be called into question, and the court should reject his attempt to minimize it.'

The special counsel argued that Flynn, a veteran US official, 'does not need to be warned it is a crime to lie to federal agents, to know the importance of telling them the truth'

Judge Sullivan will be trying to determine whether or not agents used coercion to obstruct Flynn's constitutional right.

Theoretically, if provided with convincing evidence that agents acted coercively, Sullivan could throw out the charges against Flynn on those grounds.

However, he has not indicated that he plans to do so, according to Fox News.

Trump's former National Security Adviser is due to be sentenced on Tuesday.

Last week Mueller's office said that Flynn's cooperation - including 19 meetings with investigators - was so extensive that he was entitled to avoid prison when he is sentenced.

Mueller reiterated this desire in his Friday court filling, writing that if Flynn '"continues to accept responsibility for his actions, his cooperation and military service continue to justify' no prison time.

Flynn's lawyers also asked a judge to spare him prison, saying he had devoted his career to his country and taken responsibility for an 'uncharacteristic error in judgment.'

Flynn was fired by President Trump in February 2017 for misleading the White House about his secret business meetings with senior Russian officials.

He later pleaded guilty to lying to the FBI about conversations during the presidential transition period with the then-Russian ambassador to the United States, Sergey Kislyak.

Asked about the contents of these conversations during the interview at his office in the White House in the days following Trump's inauguration, Flynn told agents he did not discuss sanctions with Kislyak.

However an audio recording of the December 29, 2016 phone call, which was tapped by US intelligence officials, proved he had.

Flynn will become the first White House official punished in the Special Counsel's ongoing probe into whether the Trump campaign coordinated with Russia during the 2016 presidential election.

In court papers Tuesday, he requested probation and community service for his false statements.

The filing comes as lawyers for former Trump campaign chairman Paul Manafort said they were still deciding whether to dispute allegations that he lied to investigators and breached his plea agreement.

A judge gave Manafort until January 7 to respond to prosecutors' claims that he misled them about his interactions with an associate who they say has ties to Russian intelligence and with Trump administration officials.

Flynn pleaded guilty to lying to the FBI over statements he made about meeting the then-ambassador of Russia during the Trump transition

The defendants, their fortunes sliding in opposite directions, represent starkly different paths in Mueller's investigation - a model cooperator on one end and, prosecutors say, a dishonest and resistant witness on the other.

Even as prosecutors recommend no prison time for Flynn, they've left open the possibility they may seek additional charges against Manafort, who is already facing years in prison.

Given both men's extensive conversations with prosecutors, and their involvement in key episodes under scrutiny, the pair could pose a threat to Trump, who in addition to Mueller's investigation is entangled in a separate probe by prosecutors in New York into hush-money payments made during the campaign to two women who say they had affairs with the president.

Since his guilty plea a year ago, Flynn has stayed largely out of the public eye and refrained from discussing the Russia investigation despite encouragement from his supporters to take an aggressive stance.

Flynn, a retired Army lieutenant general, spent three decades in the military, including five years in combat.

Flynn will become the first White House official punished in the Special Counsel's ongoing probe into whether the Trump campaign coordinated with Russia during the 2016 election

In a public statement after his plea, Flynn has said he cooperated with prosecutors because it was in 'the best interests of my family and our country.'

In Manafort's case, prosecutors have accused him of repeatedly lying to them even after he agreed to cooperate.

They say Manafort lied about his interactions with a longtime associate they say has ties to Russian intelligence, his contacts with Trump administration officials, and other matters under investigation by the Justice Department.

Manafort pleaded guilty to conspiracy charges in Washington in September and faces sentencing in a separate case in Virginia, where he was convicted of eight felony counts related to his efforts to hide millions of dollars he earned from Ukrainian political consulting from the IRS.