"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."

The note offered the first real glimpse into the deliberations and suggested jurors were discussing Libby's memory. Prosecutors say he lied about conversations he had with reporters regarding outed CIA operative Valerie Plame.

Libby said he told investigators his best recollection of those conversations and never intentionally lied.

Jurors resume work on Monday.

U.S. District Judge Reggie Walton granted their request to leave three hours early Friday to attend to personal, professional and medical obligations.

The seven women and four men got the case near midday on Feb. 22. They normally work from 9 a.m. to 5 p.m., but on three of the eight days they've had the case, court or personal business have shortened their deliberation time by several hours.

Libby, the former chief of staff to Vice President Dick Cheney, is accused of obstruction of justice and lying to the FBI and a grand jury about how learned and whom he told the identity of Plame, wife of prominent Iraq war critic Joseph Wilson.

Jurors have asked only one substantive question—involving Libby's discussions with Time magazine reporter Matthew Cooper—but resolved it themselves before the judge could answer.

Libby faces up to 30 years in prison if convicted of all five charges, but would surely get far less time under federal sentencing guidelines.

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Associated Press writer Matt Apuzzo contributed to this report.

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