But a misstatement doesn't always rise to the level of a crime. After all, it's hard for anyone to keep facts straight about conversations and decisions made months or even years ago. One person's recollection of events is often at odds with another's. That can make it risky for prosecutors to bring a case on the strength of false statements alone.
For example, U.S. prosecutors recently decided to drop their case entirely against Sen. Robert Menendez, Democrat of New Jersey, after a judge tossed out other counts and left only those related to gifts and alleged false statements.
A misstatement could indeed be called an oversight. The president's son-in-law and senior adviser, Jared Kushner, for example, has revised his disclosure form for national security clearance multiple times to account for previously unreported meetings with foreign contacts. His lawyer called at least one of those changes an "administrative error."
That's why most false statements cases are based on repeated lies that are material to the government's investigation, Koenig said. "There's a distinction between knowingly and purposefully lying to federal agents and simply being mistaken," he said.
Some lawyers have drawn parallels between the Russia inquiry and the special counsel investigation into the unauthorized disclosure of CIA agent Valerie Plame's name by officials in the George W. Bush administration. Special counsel Patrick Fitzgerald never charged the leaker in the investigation, but he brought a five-count indictment against I. Lewis Scooter Libby, Vice President Dick Cheney's chief of staff, for lying to investigators and a grand jury.
In announcing the charges against Libby, Fitzgerald pushed back against criticism from Republican circles that Libby was being prosecuted based on technicalities.
"Our jobs -- the criminal justice system -- is to make sure people tell us the truth," Fitzgerald told reporters at the time. "And when it's a high-level official and a very sensitive investigation, it is a very, very serious matter that no one should take lightly."
The case against Libby began with what he told investigators during an interview and later to a grand jury. He was convicted of making false statements, obstructing justice and perjury.
The Russia investigation could wind up in a similar spot, with cases against individuals for attempting to obstruct the probe proving easier to establish than showing that Trump allies colluded with Russia, said Peter Zeidenberg, who worked as a prosecutor on the Plame investigation.
"You have a cover-up because of what may or may not be illegal," said Zeidenberg, a partner at Arent Fox LLP.
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