But how can interrogators get them to give up the most sensitive information? Many intelligence analysts say the quickest way may be to administer the controversial drugs known as truth serum.
Though their use would be unlikely for prisoners of war due to international laws, al Qaeda prisoners are considered by the U.S. to be unlawful combatants - a status that does not guarantee the same legal protections.
Among those who say the so-called truth drugs should be used on al Qaeda prisoners -- if they're not already -- is the man in our story, Jed Babbin. He was deputy undersecretary of defense during the first Bush administration. Correspondent Vicki Mabrey reports.
"The question really comes down to, 'Can we get the information that will protect us from an imminent terrorist attack?' That is the number one question. If we have a person who may have that kind of information, we would be very foolish to not pursue it through a chemical interrogation."
He believes his view is shared by others in the military and intelligence communications. "I would suspect that there's fairly widespread support, accompanied by a healthy dose of skepticism."
Not much is publicly known about the use of so-called truth drugs on hostile prisoners, but there is some experience in criminal cases; they've been used periodically by defense attorneys.
Andres English-Howard said he couldn't remember the night his girlfriend, 27-year-old Andrea O'Donnell, was found strangled in their apartment in San Diego. English-Howard was charged with her death. But despite the evidence against him, he insisted he was innocent.
His lawyer, Marc Carlos, was left searching for information to use in his defense.
Although the results aren't admissible in court, Carlos brought in a doctor, Mark Kalish, who had used truth drugs before.
"He said it was like giving somebody four or five drinks," says Carlos. "When you drink, you are more apt to tell people something. You are more apt to open up. If you're given a drug and all of a sudden you are drunk, your senses are diminished. You can't really defend against prodding questions."
What we think of as truth serum can be one of a dozen drugs, including barbiturates like sodium amytal, pentothal and brevital. Commonly used as a form of anesthesia, they became known as truth serum in the early 1900s after doctors noticed patients blurting out excessively candid remarks.
In English-Howard's case, the drug took effect almost immediately. As he slipped into an uninhibited state, Dr. Kalish asked several casual questions, a technique designed to create trust between the subject and the interrogator.
Q: What sort of things would you do?
A: Whatever I wanted to. I always control my relationships.
Q: In what way?
A: My personality is pretty dominant. I find women who need something.
After 20 minutes, English-Howard slurred his speech, a signal to Kalish that it was time to intensify the interrogation and ask about the night of the murder. Under intense questioning, English-Howard admitted he came home high on crack cocaine and Andrea was angry.
Disoriented by the truth serum, English-Howard rambled through unrelated and related details of that night. With Carlos standing by, Kalish methodically directed him back on track.
Q: Then what happened?
A: I just sat listening to her and I wanted to shut her up…so the next thing I knew, I was on her. I grabbed her.
Q: Where did you grab her?
A: I grabbed her neck.
"He said, 'I just was on her, and the second I was on her, I started grabbing her,'" remembers Carlos. "And it was over, with his hands around her throat. I thought that's what happened."
Carlos believed that what English-Howard described while he was under the sodium brevitol was the truth.
"I mean, it was his truth," says Carlos. "And it wasn't too far from what probably happened."
A year later, English-Howard confessed on the stand, and then hanged himself in his cell after being convicted of murder.
However, it may not have been as simple as a drug that forced English-Howard to confess. His lawyer thinks the drug tapped into his guilty conscience, which would be highly unlikely to happen to a hardened terrorist.
But Babbin says truth drugs may succeed in lowering the inhibitions of an al Qaeda operative, just enough for him to blurt out something useful.
"I hate the term 'truth serum' because there really is no such thing," says Babbin. "But there are a number of chemical relaxants. Basically, they are depressants. They will take a normal person's pain threshold, and pretty much eliminate it. They will make you a little bit drunk, and a little bit happy."
Making a suspect disoriented and vulnerable is the goal of interrogators. When the U.S. captured suspected al Qaeda members, they were hooded and bound in awkward positions to further intimidate them during transport to Guantanamo Bay, Cuba.
At the Bagram Air Base interrogation center in Afghanistan, it's been reported that the U.S. is using other disorientation techniques - from sleep deprivation to temporarily withholding food and water.
There are some concerns that these techniques are already going too far, and that the use of truth drugs would be a form of torture. Babbin disagrees.
"If you torture someone, you're inflicting pain. Possibly permanent damage," adds Babbin. "Quite frankly, so called truth drugs, if used properly, under medical supervision, are completely safe."
"It is invasive, but it is not wrong. The real issue is what risks we are willing to take - with our own women, children, people all around the country."
Due to the Geneva Conventions, prisoners of war are unlikely to be subject to chemical interrogations. However, the U.S. considers al Qaeda members unlawful combatants which means they are not guaranteed the same protections.
And while officials have said the U.S. is not using truth drugs in interrogations, there are reports that scores of captives have been handed off to countries thought to use truth drugs.
Does Babbin believe that, at this moment, there are al Qaeda prisoners on whom truth drugs are being used?
"I can't say that there are. I do sincerely hope they are," says Babbin, who doesn't think he's alone with that opinion. "A lot of other folks in and around the military are saying, 'This is something we ought to at least try and determine if it can work reliably.'"
The reliability of truth drugs is hard to determine. The countries thought to use them do so in secret, and the U.S. hasn't been known to conduct truth drug experiments since the Cold War, when the government dismissed them as unreliable.
Doctors who've conducted truth drug interviews have also said it's not a magical elixir that forces the truth to just come out when a subject's inhibitions are lowered. They say you'll sometimes get bits of the truth, mixed with fantasy or even lies.
One person who knows firsthand about hostile interrogations under truth serum is Oleg Gordievsky. One of the KGB's top spies, he was a double agent for 11 years, secretly working for the British Intelligence Service.
In 1985, he got a cable from his bosses in Moscow, telling him to return quickly to Moscow to meet with his superiors.
"I had a very, very bad feeling about it," says Gordievsky.
Nervously, he returned to Moscow and waited. After eight days, he says he was summoned for a meeting at a bungalow outside the main KGB compound. There were three KGB generals there who asked him to join them for lunch.
"They poured such a glass, tiny glass, of the Armenian brandy into my glass," remembers Gordievsky. "Then they said, 'OK, OK, Good health. Good health. Let's have another interesting discussion.' I drank my brandy. And it was like you're on a table being operated on in the hospital. The reaction was immediate."
He says his brandy was laced with a truth drug. His story was later backed up by another KGB defector.
At the time, Gordievsky remembers being very excited, being full of ideas, wanting to argue and talking endlessly.
"They kept asking me questions," says Gordievsky. "They wanted me to admit that I was a British spy."
"And I was saying, 'No. What British spy? What are you talking about.' I kept denying and kept denying."
Even Babbin admits that people can successfully resist truth drugs and could be spouting jibberish. But buried in the statements of one al Qaeda prisoner's interrogation, Babbin says, may lie the one clue that could save hundreds, or even thousands of lives.
Al Qaeda clearly fears truth serum - even warning against truth serum. In its training manual, "Military Courses in the Jihad Against the Despots," operatives are advised to be on guard for "a narcotic that can weaken a brother's willpower."
Babbin believe the fear of truth serum alone may be enough to unlock al Qaeda's secrets.
"They're terrified of what the result might be, and terrified of losing control," says Babbin.
"All you can do is get as much information as you can, start checking it against other information, and seeing if it is coincident with the other things you're finding out. In which case, it may be of great value."