"I’m not scared of what [terror mastermind] Khalid Sheik Mohammed has to say at trial — and no one else needs to be either," Holder said.
He said previously undisclosed evidence against the al Qaeda terror suspects would all but guarantee convictions.
But he was pressed by Republicans on the Senate Judiciary Committee, who said the decision to take the trials away from a military commission was "dangerous" and "misguided."
But Mohammed has announced to the world he wants to plead guilty before a military commission, he said.
"How could he be more likely to get a conviction than that?" Kyl demanded.
"These trials do not hinge on the desire of Khalid Sheik Mohammed," Holder shot back. "He will not select the prosecution venue. I will — and I have."
After the hearing, Holder was confronted by Alice Hoagland, whose son died on 9/11 aboard hijacked Flight 93.
"I take great exception to your decision to give short shrift to the military commissions and put the most heinous criminals .¤.¤. on trial in New York City," she said. "I can’t help thinking that it does make New York City a more dangerous place and a target."
Holder assured her that he considered all her concerns. "I think what we have done is put in motion a process that will finally, finally resolve these matters," he said.
Also yesterday, former Mayor Rudy Giuliani said holding the trials in New York would tell the world that America is "on defense" in the war on terror.
"One of the best things the Bush Administration did was put us on offense," the former mayor told reporters. "Putting us back on defense puts us in a very vulnerable position, not just in New York, but nationally."
During the Senate hearing Sen. Chuck Schumer pressed Holder for a guarantee that the city will be reimbursed for the cost — estimated at $75 million a year — for providing security during the trials.
Holder said he would ask President Obama for the money.
Obama, who said Holder alone made the trial decision, defended it in a series of TV interviews.
"(What) I think we have to break is this fearful notion that somehow our justice system can’t handle these guys," Obama told NBC News.