President Donald Trump. REUTERS/Carlos Barria President Donald Trump last year slammed Hillary Clinton staffers who requested immunity or invoked their Fifth Amendment rights in response to requests to testify about the former secretary of state's private email server.

"If you are not guilty of a crime, what do you need immunity for?" Trump said at a campaign rally in Florida in September.

"The mob takes the Fifth Amendment," Trump said at a campaign event in Iowa later that month. "If you're innocent, why are you taking the Fifth Amendment?"

That was then.

Trump's former national security adviser, Michael Flynn, in March requested immunity from prosecution in exchange for testifying before the House and Senate intelligence committees about Russia's interference in the 2016 election. And on Monday, Flynn is expected to flout a Senate subpoena for documents related to his contacts with Russia by invoking his Fifth Amendment rights against self-incrimination.

The White House press secretary, Sean Spicer, has also weighed in on the amendment, tweeting in 2013, "Why do u take the 5th if you have done nothing wrong and have nothing to hide?"

Flynn himself said during an interview last year with MSNBC commentator Chuck Todd, "When you are given immunity, that means you have probably committed a crime."

"It's conceivable that Flynn is innocent," Glenn Carle, a former CIA operative who worked closely with the FBI during his time as an intelligence officer, said shortly after Flynn requested immunity. "But the FBI is extremely powerful and has sources everywhere. So assuming Flynn is asking for immunity because he thinks he did something wrong and wants to save his own ass, the bureau will probably say, 'Thanks, but no — why should we do you a favor if we don't even need your testimony?'"

Rep. Eric Swalwell, a Democrat who sits on the House Intelligence Committee, would not comment on whether the committee had agreed to Flynn's immunity request. But he hinted in an interview last week that it might not need the story that Flynn's attorney has said he is eager to tell.

"Speaking as a former prosecutor," Swalwell said, "you would only offer immunity to a witness who could provide testimony you could not otherwise obtain."

Flynn's ties to Russia have been of particular interest to the congressional intelligence committees because of his conversations with Russia's ambassador to the US, Sergey Kislyak, that eventually led to his ouster. CNN on Friday reported that Russian officials boasted of their relationship with Flynn throughout 2016. They saw him as an ally who could help Moscow make inroads with Trump, said the report, citing unnamed sources.

According to NBC, Flynn also is a focus of a criminal investigation by the FBI, which is examining whether his failure to disclose several foreign relationships on his security clearance forms violated federal law.

The former general's baggage is well-known. President Barack Obama fired him as head of the Defense Intelligence Agency in 2014, and he sat next to Russian President Vladimir Putin at a dinner celebrating Russia Today's 10th anniversary in 2015.

Still, Trump's family had a "blind spot" for Flynn, according to NBC, and reportedly hired him even after he informed the transition team that the FBI was investigating him because of his lobbying work for Turkey.

Flynn's time at the White House lasted just 24 days. He was asked to resign on February 13 — nearly three weeks after the acting attorney general, Sally Yates, warned the White House that Flynn could be vulnerable to Russian blackmail — amid reports that he had discussed sanctions with Kislyak during the transition.

But Trump continued to defend him, going as far as suggesting to James Comey, the FBI director, the day after Flynn resigned to drop the investigation into Flynn's foreign contacts, according to a memo Comey wrote about the conversation.

Reuters reported Thursday that the Trump campaign had at least 18 previously undisclosed contacts with Russian officials during the election, six of which were between Flynn and Kislyak. The two were trying to establish a "back channel" between Trump and Putin "that could bypass the US national security bureaucracy," according to Reuters.