"We just had a four-star general, highly respected, Gen. (James) Cartwright, heard what happened yesterday. Could go to jail for five years because he supposedly told a lie to the FBI. And I don't know that it was even a lie. I don't know," Trump said at his last of three campaign rallies on Friday.
Cartwright, a retired Marine Corps general, pleaded guilty on Monday to a charge of making false statements to federal investigators following an investigation into whether he leaked classified information to a reporter.
Trump has pounced on the case to argue there has been a double standard in the FBI and Department of Justice's prosecution of such cases, citing the Justice Department's decision over the summer not to file criminal charges in the case of Hillary Clinton's private email server.
But Trump on Friday took his criticism of the federal criminal justice system a step further by suggesting that Cartwright may not have actually lied to federal investigators.
That suggestion flies in the face of Cartwright's guilty plea in federal court and comes on the heels of Trump arguing that the presidential election is "rigged" and rejecting the US intelligence community's conclusions that Russia has been behind a series of hacks of Democratic officials' emails -- all comments that could erode public trust in key US government institutions.
"So you are pleading guilty because you are, in fact, guilty?" US District Court Judge Richard Leon asked Cartwright in court on Monday.
"Yes, sir," Cartwright answered under oath.
Trump's campaign did not immediately respond to a request for comment about why Trump was questioning Cartwright's guilty plea or whether he was suggesting federal officials coerced Cartwright into admitting guilt.
But Trump's remarks Friday evening fit a familiar pattern that the GOP nominee has increasingly laid out in recent weeks as his campaign has undergone its most tumultuous period.
Beyond suggesting that the election is "rigged," Trump has repeatedly argued there is an establishment conspiracy looking to sink his campaign, warned his supporters about voter fraud on Election Day -- overstating those extremely rare occurrences -- and refused to pledge to abide by the results of the presidential election, even if he should lose.
"I will look at it at the time," Trump said at the GOP debate on Wednesday after he was asked whether he would concede the election should he lose.
Even as he sought to clean up that response the next day by saying he would "accept a clear election result," Trump continued to cast on the legitimacy of the results by saying he was reserving his "right to contest or fie a legal challenge."
And as he's been pressed in recent weeks over the hacking of Democratic officials' emails, which US officials have said Russian intelligence services are responsible, Trump has refused to accept that conclusion, instead saying he was not convinced Russia was responsible and suggesting it could even be "a 400-pound man." Those remarks come even as Trump has received two classified intelligence briefings from US officials.
Trump's criticism of the FBI predates the Cartwright case.
The Republican nominee has for months alleged that the heads of the FBI and Department of Justice colluded with the Clintons to save the former secretary of state from prosecution, rather than accepting the Justice Department's decision.
But the Cartwright case has provided Trump with fresh fodder to continue to do so.
"What happened to the FBI, I don't know," Trump said during the debate on Wednesday. "We have a great general, four-star general ... going to potentially serve five years in jail for lying to the FBI, one lie. She's lied hundreds of times to the people, to Congress and to the FBI. He's going to probably go to jail ... and she gets away with it and she can run for the presidency of the United States?"
While Cartwright pleaded guilty to a charge that carries a maximum five-year prison sentence, his plea agreement states that he should face no more than six months in prison.