WASHINGTON (Reuters) - U.S. President Donald Trump’s former national security adviser Michael Flynn appeared in court on Monday for the first time since hiring a new lawyer who has criticized Special Counsel Robert Mueller’s investigation into Russian interference in the 2016 election.

The lawyer, Sidney Powell, told U.S. District Court Judge Emmet Sullivan that the evidence in the case has “more moving pieces ... than an old-fashioned Swiss watch.” Powell, who took over Flynn’s case earlier this month after he fired his previous lawyers, said she may need to seek a security clearance to review classified information to help Flynn prepare for his sentencing for lying to investigators.

Powell frequently appears on Fox News and sells t-shirts saying “Creeps on a Mission” featuring images of Mueller, former FBI Director James Comey and other Justice Department officials.

She is also the author of a book called “Licensed to Lie: Exposing Corruption in the Department of Justice” and Sullivan said she sent him a copy in 2014 with a note praising his service as a judge.

Sullivan said he decided he should disclose receiving a signed copy of the book and that it did not warrant him recusing himself from the case.

Flynn was among the first people in Trump’s inner circle to be charged by Mueller’s prosecutors for lying to investigators about his December 2016 conversations with Sergei Kislyak, Russia’s then-ambassador in Washington, about U.S. sanctions imposed on Moscow by President Barack Obama.

Flynn worked on Trump’s election campaign and the conversations took place between Trump’s November election victory and his January 2017 inauguration.

He pleaded guilty to the charge, agreed to cooperate with Mueller’s investigation and has assisted prosecutors in a separate federal case against his former business partner, Bijan Rafiekian.

Flynn, who lasted less than a month as Trump’s national security adviser, was supposed to be sentenced in December but that was postponed after a contentious hearing in which Sullivan excoriated Flynn for lying to investigators, and accused the retired U.S. Army lieutenant general of selling out the United States.

Former U.S. national security adviser Michael Flynn departs after his sentencing was delayed at U.S. District Court in Washington, U.S., December 18, 2018. REUTERS/Joshua Roberts

A new sentencing date has not been set.

Sullivan then gave Flynn the option to have his sentencing delayed so that he could fully cooperate with any pending investigations to help bolster his case for leniency.

It is unclear whether Flynn will change his legal strategy before his sentencing.

Powell has written opinion pieces in which she called for Flynn to consider withdrawing his guilty plea. However, after Flynn hired her she said in a statement that Flynn would “continue to cooperate with the government in all matters.”

Powell confirmed Monday that Flynn’s cooperation with the government is “fully ongoing” and that he is expecting to testify in Rafiekian’s trial in July.

Rafiekian was indicted on allegations of unregistered lobbying on behalf of Turkey. Rafiekian denies the charge.

The government disputed her claim that she will need a security clearance to review classified material prior to sentencing.

“There is no classified discovery provided to defense counsel,” prosecutor Brandon Van Grack said. He said the discovery file is only about 20,000 pages.

“We are not talking terabytes of data,” he said.

Powell said she will need 90 days before being able to provide the court with an update but Sullivan set a 60-day deadline for the end of August to receive a status report.

(This story refiles to fix typo in headline)