(CNN) The Justice Department's handling of former Trump national security adviser Michael Flynn's case is a "gross abuse of prosecutorial power," a court-appointed attorney and former judge wrote in a searing 82-page analysis on Wednesday.
The court-appointed lawyer John Gleeson also argued that Flynn should be sentenced for lying, including for perjuring himself in court for admitting his crimes then disavowing them.
Gleeson, looking at Flynn's full case record, reasoned that the Justice Department's recent support of Flynn is so politically advantageous to President Donald Trump and atypical for prosecutors, it's undermined the public's trust in the rule of law.
"The facts surrounding the filing of the Government's motion constitute clear evidence of gross prosecutorial abuse. They reveal an unconvincing effort to disguise as legitimate a decision to dismiss that is based solely on the fact that Flynn is a political ally of President Trump," Gleeson wrote to US District Judge Emmet Sullivan on Wednesday.
The Justice Department "abdicated that responsibility" to prosecute defendants without fear or favor, Gleeson wrote, by "attempting to provide special treatment to a favored friend and political ally of the President of the United States," capturing what many critics of Attorney General William Barr and Trump, especially in the legal community, have alleged.
"It has treated the case like no other, and in doing so has undermined the public's confidence in the rule of law," he wrote.
Gleeson made the argument on Wednesday after Sullivan requested his analysis on Flynn's statements under oath, and asked him to argue against the Justice Department's request to drop Flynn's case.
Gleeson's filing highlights the unusual territory the Flynn court case has waded into and the legal questions Sullivan is now weighing. Flynn is also trying to short-circuit Sullivan's consideration of the case, prompting the DC Circuit Court of Appeals to also consider the questions of whether Gleeson can weigh in on the case and whether the case must be dismissed immediately.
Flynn pleaded guilty before two federal judges to lying to the FBI about his contacts with the Russian ambassador in late 2016, when he asked Russia not to retaliate for Obama administration sanctions for election interference and to split from the Obama administration on an upcoming UN vote on Israel. He cooperated for a year in interviews with the special counsel's office and a federal grand jury about his interactions with Russia and about his work in 2016 lobbying for Turkey, before renouncing his admissions.
Barr then decided last month to drop Flynn's charge. The Justice Department has argued Flynn's lies weren't "material" to an investigation, because Flynn should never have been under investigation for his interactions with Russian officials.
The case has become a touchstone for Trump and his supporters as they continue to criticize the Russia investigation and Mueller's criminal prosecution of several Trump campaign associates. It's also prompted critics of Barr, including Gleeson, to argue that Trump has corrupted the Justice Department's legal decisions and that Barr has bent to Trump's political wishes to undercut Mueller's work and go easy on his former advisers.
Sullivan, in handling Flynn's case at the trial level, has hesitated to dismiss the charge.
Gleeson on Wednesday said it wasn't necessary for Sullivan to consider holding Flynn in criminal contempt for perjury. Instead, the judge could factor in Flynn's obstruction of his court proceedings as part of his sentence.
Gleeson slammed Flynn for trying to claim innocence two years after he signed his plea deal.
"A false eleventh-hour disavowal of a plea and a trumped-up accusation of government misconduct constitute obstruction of the administration of justice," Gleeson wrote.
"Flynn did not simply seek to withdraw his plea, but did so by mounting a frontal assault on the integrity of the investigation. This was deliberately obstructive ... Flynn's apparent attempt to manipulate the system is particularly stark given the circumstances," he added, noting Flynn's history as a US Army general and top intelligence official. "He ranks among the savviest of criminal defendants to come before any court."
Sullivan giving a sentence to Flynn -- which could range from no prison time to a maximum of five years in prison -- would be a way to restore order to the justice system, Gleeson wrote. Sullivan previously indicated he believed Flynn deserves jail time.
Several supporters of Trump and of Flynn -- including the Justice Department, Republican members of Congress and Republican attorneys general -- have argued that the court must follow the DOJ's decisions on whether or not a defendant should be prosecuted. They've argued for the case to be dismissed quickly, without Flynn being sentenced.
Some, including his legal defense team, have also publicly implored Trump to pardon Flynn.
Gleeson found the Justice Department's actions in the case raised too many questions for the judge to have to accept the case's dismissal.
Flynn is trying to stop Sullivan from delaying the Justice Department's request for dismissal, by appealing his appointment of Gleeson. A three-judge panel on the DC Circuit Court of Appeals will hear arguments about why Sullivan should or shouldn't still have control of the case this Friday.
Gleeson served as a federal judge in the Eastern District of New York for 22 years and is now a partner in New York with the elite defense law firm Debevoise & Plimpton. Before Sullivan appointed him, he co-authored an op-ed in the Washington Post arguing for Sullivan to keep control of the Flynn case, questioning the Justice Department's actions in it.
The Democrats on the House Judiciary Committee on Wednesday filed a brief with Sullivan lashing out at Barr for his handling of several politically charged matters.
"There may be a perfectly legitimate explanation for the government's change of heart. But the facts currently available to the public, the Committee, and this Court evoke corruption," they write. "It is the role of this Court to bring that truth to light."
The Democrats also highlight how Barr has blocked them from investigating him.
"The need for judicial oversight is even more pronounced because Attorney General Barr has stonewalled congressional oversight at every turn, depriving the House Judiciary Committee of any opportunity to question Barr about his mischaracterization of the Mueller Report, his role in the sentencing of Roger Stone, or the policies he has put in place to facilitate the improper politicization of prosecutorial decision-making," they write. "Barr now seeks to stonewall this Court, too."
Sullivan wrote on Wednesday that he hasn't decided what to do with Flynn's case.
"Despite the assumptions underlying Mr. Flynn's and the government's briefs, Judge Sullivan has not decided to deny the motion to dismiss or to proceed with a contempt inquiry. All he has decided is that there may be something to decide," Sullivan wrote in a brief to the DC Circuit in advance of the court's hearing about his power.
Sullivan highlighted another politicized court case in his argument to make his point: an appeal attempt by Roger Stone, Trump's longtime friend and political adviser. The DC Circuit had denied Stone's attempt to challenge his gag order before his criminal trial, and Sullivan argued on Wednesday that the appeals court's ruling in that case is a reason for the Circuit to stay out of the Flynn case now too.
The Justice Department and Flynn also made their final arguments to the Circuit on Wednesday, saying the Justice Department holds the power in prosecutorial decisions. Both are asking the DC Circuit to force Sullivan, the trial-level judge below them, to dismiss Flynn's case.
The arguments, taken together, reflect how intense the Flynn case has become, especially as it heads into the hearing Friday, with the appeals court grappling with questions about the separation of powers and the checks and balances judges may have on the executive branch.
This story has been updated with additional developments.