Judge Leonie Brinkema ruled that prosecutors cannot present evidence at trial saying Moussaoui helped plan the 2001 attacks on New York and Washington, in which about 3,000 people died.

Each of the six charges against Moussaoui is linked to the September 11 terror attacks.

Brinkema has also said that Moussaoui cannot get a fair trial unless he can question imprisoned al-Qaeda leaders as defense witnesses. In January she ruled that Moussaoui should have access to the al-Qaeda leaders, which he claims will clear him of the charges.

Federal officials have refused access to the witnesses, citing national security issues.

The judge had even considered dropping all charges against Moussaoui, as the defence has requested.

"I think it's a great decision, because it takes the death penalty off the table," said Gerald Zerkin, one of three court-appointed lawyers for the Frenchman.

Moussaoui has been conducting his own defence, but Brinkema has assigned court lawyers to help.

"I don't know what the government will do, I won't even speculate on that," Zerkin said.

Brinkema, whose court is located in the Washington suburbs of Alexandria, Virginia, "ordered that the government's Notice of Intent to seek a sentence of death and notice of special findings be and are stricken."