The trial of Lewis “Scooter” Libby, the vice-president’s former chief of staff, closed on Tuesday with prosecutors accusing him of concocting a “ludicrous” story about how he learned the name of a CIA agent, while the defence called it “madness” to convict him on the basis of a witness “suffering public memory lapses”.

Making closing arguments in the month-long perjury and obstruction of justice trial, which could see Mr Libby face up to 30 years in prison, the lawyers offered competing narratives to explain how and when Mr Libby discovered the identity of Valerie Plame, the wife of ambassador Joe Wilson who had emerged as a leading critic of the Iraq war.