They met that afternoon at the White House, and Yates, accompanied by the top career official in the Justice Department's national security division, dropped a bomb: President Trump's national security adviser, Michael Flynn, had lied to Vice President Pence about Flynn's contacts with Russian Federation.
Yates in January warned White House officials that Flynn, a retired U.S. Army general, spoke with Russian ambassador Sergey Kislyak in December, the same day the Obama administration ordered sanctions on Russia for its alleged hacking of Clinton's presidential campaign. At the time she was sacked, Yates was also a key official involved in the investigation of national security adviser Michael Flynn.
Clapper rebutted the Trump argument that Obama officials (particularly Susan Rice, who declined to appear Monday) had improperly "unmasked" Flynn or others. Was he still fulfilling his normal national security adviser duties?
Yates' view that Trump's order was unlawful and inconsistent with the principles of the Justice Department ultimately was upheld by three federal courts that blocked its enforcement; the Trump administration eventually withdrew it and replaced it with a more carefully drawn order that nevertheless also has been blocked by the federal courts.
Republican Sen. John Cornyn said her actions with regard to the executive order were "enormously disappointing" and accused her of undermining the powers of the President because she disagreed with Trump's order "as a policy matter".
Spicer said he did not know why Yates was not told about the order and could not say whether it was on objective. Eighteen days went by between Yates expressing her concerns to the White House and Flynn being removed from the post.
Worse, if it could be worse, in the days before and after Trump´s inauguration, Flynn was lying to his superiors about the nature of his dialogues with Moscow´s ambassador - and they either didn´t know or didn´t care about the nefariousness of his denials.
"Let's look at how this came down", Spicer said.
In a series of tweets on Monday evening, Mr Trump doubled down on his stance. Yates detailed her own warnings to the Trump White House about Flynn, including meetings with the White House counsel in which she said that discrepancies over Flynn's contacts with the Russian envoy left him vulnerable to blackmail by Moscow.
Spicer frequently has chided the White House press corps for failing to ask more questions about the source of illegal leaks to the press.
At just 24 days, Lt. Gen. Michael Flynn had the shortest tenure as White House National Security Adviser of anyone to ever hold that post.
In March Clapper told "Meet the Press" that as DNI, he had seen no evidence of collusion between Russian operatives and the Trump campaign team.
"We believed that General Flynn was compromised with respect to the Russians", Ms Yates told the hearing in her first public comments on the scandal, which has dogged the opening months of Mr Trump's presidency.