WASHINGTON - Classified information will be key evidence in the CIA leak trial and Special Prosecutor Patrick Fitzgerald went too far in his proposal to limit its release, a federal judge ruled Monday.

I. Lewis 'Scooter' Libby, Vice President Dick Cheney's former chief of staff, walks to the US District Court in Washington, in this Nov. 16, 2005 file photo. His attorney Theodore V. Wells Jr., is pictured behind him at rear. Special Prosecutor Patrick Fitzgerald and Libby agree on something: keeping Libby's perjury trial in the CIA leak case focused solely on his actions. The two are separately asking a federal judge not to allow three years of politically charged backstory in the case to seep into Libby's trial starting in January. [AP]

Former White House aide I. Lewis "Scooter" Libby is charged with lying to investigators in the case and wants to present classified material at his trial in January to show jurors that he had a lot on his mind and couldn't remember details about the leak.

US District Judge Reggie B. Walton said Libby has a right to use some classified material at trial in January. Walton has not said publicly what must be allowed, and both sides are arguing behind closed doors over how the information will be blacked out for jurors.

In a ruling Monday, Walton said Fitzgerald's proposed redactions were too restrictive. The memory argument is a key part of Libby's defense, Walton ruled, and he must be allowed to use classified information to make that case.

"He is alleging both that the volume of his work would have impacted his memory and that some of the information presented to him as the vice president's national security adviser was so potentially catastrophic to the well-being of the country that the focus he had to devote to this information also impacted his memory," Walton said.

Walton said he isn't going to give Libby a free pass to allow all classified information into court. He said the two sides must balance Libby's need to defend himself with the government's need to protect sensitive material - a compromise that he believed could be achieved.

Walton told Fitzgerald to "go back to the drawing board and come forth with a more balanced proposal."

Libby is charged with lying to investigators about his conversations with reporters about CIA operative Valerie Plame. Plame believes her identity was leaked to the press as retribution for her husband's criticism of prewar intelligence on Iraq.