Washington, D.C. ? Jurors asked for a definition of “reasonable doubt” as they completed a shortened eighth day of deliberations Friday in the perjury trial of ex-White House aide I. Lewis “Scooter” Libby.

They were to get an answer when they return Monday morning.

The written question the jurors sent to the judge offered the first real glimpse into the deliberations and suggested jurors were discussing Libby’s memory, a key element in his defense.

“We would like clarification of the term ‘reasonable doubt,'” jurors wrote. “Specifically, is it necessary for the government to present evidence that it is not humanly possible for someone not to recall an event in order to find guilt beyond a reasonable doubt.”

Libby, former chief of staff to Vice President Dick Cheney, is charged with lying to the FBI and a grand jury in 2003 about how he learned the identity of CIA operative Valerie Plame and whom he told about it.