Factbox - Did Comey's testimony support an obstruction of justice charge?

Former FBI Director James Comey testifies before a Senate Intelligence Committee hearing on Russia's alleged interference in the 2016 U.S. presidential election on Capitol Hill in Washington, U.S., June 8, 2017. REUTERS/Jonathan Ernst

(Reuters) - By saying he believed Donald Trump directed him to end a probe into a former national security adviser, former FBI Director James Comey added fuel on Thursday to critics' accusations that the U.S. president engaged in obstruction of justice.

Such an offence could be the basis for eventual impeachment proceedings against Trump. But proving obstruction of justice is far from clear-cut, because it hinges on intent, and legal experts differed sharply on whether it might apply to Trump and his dealings with Comey and the FBI probe.