Anyone who says America's federal courts can't bring terrorists to justice is overlooking the facts. In the Dirksen U.S. Courthouse in Chicago on March 18, David Headley pleaded guilty to a dozen terror-related felonies, including helping plan the 2008 attacks in Mumbai, India, that killed 164 people. He is also providing authorities with valuable intelligence about terrorist activities, according to the Justice Department.

Wearing leg shackles and heavily guarded by U.S. marshals, Headley admitted to scouting sites in Mumbai for the Pakistan-based terror group Lashkar-e-Tayyiba, and to plotting to attack a Danish newspaper. He faces life imprisonment when he is eventually sentenced for his crimes.

His guilty plea and his cooperation are significant victories for justice and our intelligence agencies. They demonstrate that federal criminal courts -- also called Article III courts in reference to the article of the Constitution establishing the federal judiciary -- can effectively prosecute terrorists and gather intelligence.

Some of the most well-known terrorists of the past decade -- "Shoe Bomber" Richard Reid, "Blind Sheik" Omar Abdel Rahman and the "20th Hijacker" Zacarias Moussaoui -- are serving life sentences after being tried in Article III criminal courts. Military commissions have prosecuted just three Guantanamo detainees since 9/11. Two of these terrorists served light sentences and are free.

This contrast between life sentences and light sentences leaves no doubt that federal criminal courts effectively punish terrorists.

There may be times when a military commission is the best venue for a trial. But the president should have the flexibility to choose which system in which to prosecute. The decision should hinge on which system is most likely to produce actionable intelligence, protect our national security, bring terrorists to justice quickly, and keep them behind bars for good. Prosecutions in Article III courts can achieve all of these objectives.

For example, Najibullah Zazi, accused of plotting to bomb New York City's subway system, pleaded guilty in federal court on Feb. 22 and is reported to be cooperating. In the case of 9/11 mastermind Khalid Sheikh Mohammed, the attorney general is confident that prosecutors can secure a conviction and a death sentence in federal court.

Hundreds of international terrorists have been convicted in our federal courts since 9/11 and are locked away in heavily fortified federal prisons. Federal courts are tried, tested and capable of dealing with extremely dangerous defendants and classified intelligence. In contrast, military commissions are slow, untested and have not yet overseen a death penalty trial since 9/11.

President Obama's fear-mongering critics make three false accusations in their bid to discredit America's federal courts:

-- First, they claim terrorists will have access to classified evidence. But the Classified Information Procedures Act sets up a process for federal judges to protect classified information during terrorist trials. The rules for how military commissions treat classified information are based on the rules used in federal criminal courts.

-- Second, they claim federal prosecutors can't properly try terrorists. Yet federal prosecutors have more experience handling terrorists than anyone else. According to a Bush-era Department of Justice document, "Since September 11, 2001, the Department has charged 512 individuals with terrorism or terrorism-related crimes and convicted or obtained guilty pleas in 319 terrorism-related and anti-terrorism cases." That's far more than the three convictions in military commissions.

-- Finally, they claim federal courts allow terrorists to take advantage of constitutional requirements for Miranda warnings and search warrants. But it is simply wrong to claim that a search warrant is required to obtain physical evidence from overseas, or that a criminal prosecution requires that detainees be immediately given Miranda warnings.

The record speaks for itself: Our criminal justice system is very effective at punishing terrorists. Headley's guilty plea in an Article III court has provided the most recent evidence of this. Headley admitted his crimes, is providing intelligence, and is likely to spend the rest of his life in federal prison. Case closed.

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Mrs. Feinstein, a Democrat, is a U.S. senator from California and chairman of the Senate Intelligence Committee.