Washington (CNN) Former national security adviser Michael Flynn, the only former Trump administration official so far charged in the Russia investigation, will be in court Tuesday for a procedural hearing about his sentencing -- his first court appearance since he admitted that he lied to investigators seven months ago.

Federal Judge Emmet Sullivan last week ordered Flynn and the prosecutors working for special counsel Robert Mueller back to court to hash out some details regarding Flynn's sentencing. He pleaded guilty in December to lying to the FBI, but his sentencing has been delayed while he aided the Mueller probe.

The question at hand: Why do Flynn's lawyers and Mueller's team want to move forward with steps usually reserved for the sentencing phase while simultaneously asking to delay sentencing?

The two parties jointly asked that a probation officer prepare a report on how Flynn's background fits with federal sentencing guidelines. They also asked that sentencing be delayed for another two months. They told Sullivan this was necessary "due to the status of the Special Counsel's investigation," but that explanation was not enough to satisfy the judge, who is known for strong oversight of prosecutors.

Some conservative activists have called for a "flash mob" of Flynn supporters to gather outside the courthouse Tuesday morning. Conservative groups online have recently promoted, without evidence, rumors that the case against Flynn was collapsing and that Flynn might withdraw his guilty plea.

Read More