There has been "one atrocity after the other" in the case of former U.S. national security adviser Michael Flynn, his defense attorney said Friday during an appearance on Fox News' "Hannity."

In January, Flynn filed a motion to withdraw his guilty plea for lying to the FBI in the Russia investigation, claiming the government had acted in "bad faith."

DOJ TAPS OUTSIDE PROSECUTOR TO REVIEW HANDLING OF FLYNN CASE

Defense attorney Sidney Powell claimed Friday that a group of FBI officials had worked together in early 2017 to determine "how and when" to interview Flynn in a way that would keep him from knowing he was the subject of an investigation.

She named some of those officials as then-FBI Deputy Director Andrew McCabe, onetime counterespionage section chief Peter Strzok and Trisha Anderson, a former second-in-command at the bureau's Office of General Counsel.

"So not only was he not warned of his rights, he didn't even know that he was being investigated," Powell told host Sean Hannity. "In fact, he was led to believe that he wasn't being investigated."

"Not only was [Michael Flynn] not warned of his rights, he didn't even know that he was being investigated. In fact, he was led to believe that he wasn't being investigated."
— Sidney Powell, attorney for Michael Flynn

Powell added that Flynn's case was the first instance she had heard of in which a defendant accused of making false statements to the FBI was not warned of his rights or informed that he was under investigation.

FLYNN ATTORNEY DEMANDS FBI SEARCH 'SENTINEL' DATABASE FOR MISSING, 'MANIPULATED' WITNESS REPORTS

In November of last year, Powell demanded that the FBI turn over "every" document in which agents described the January 2017 interview that led to Flynn being charged after a separate filing in October accused agents of manipulating the form used to report on or summarize witness interviews, known as a "302 form."

"They say they can't find [it], he can't produce it [the 302 form]," she said of Flynn prosecutor Brandon Van Grack, who she claimed has a separate conflict of interest in the case.

"There is one atrocity after the other in this case."

Powell asserted that the 302 form was altered to indicate that Flynn had answered "no" when asked if then-Russian ambassador to the U.S. Sergey Kislyak "described any Russian response to a request by Flynn." But Strzok's contemporaneous notes do not mention a "Russian response" at all, Powell observed.

The FBI has argued that an apparently missing version of the Flynn 302, drafted before February 2017, did not need to be produced because “there is no reason to believe it would materially differ” from material provided to Flynn's legal team. But, Powell wrote, the law on intentional or unintentional evidence spoliation, or destruction, is clear, and "requires the assumption that the evidence is favorable to the defense."

Earlier Friday, a senior Justice Department official told Fox News that Jeff Jensen, the U.S. Attorney for the Eastern District of Missouri, has been assigned to Flynn’s case.

CLICK HERE TO GET THE FOX NEWS APP

Jensen will be working hand-in-hand with Van Grack, according to the official.

Flynn's sentencing has been postponed repeatedly over the last two years. His supporters have insisted he is innocent but was forced to plead guilty when his son was threatened with prosecution and he exhausted his financial resources.

Fox News' Gregg Re, Jake Gibson, Andrew O'Reilly and Brooke Singman contributed to this report.