Alice Hoglan has been on the talk-radio circuit this month, explaining why she is about to travel from her home in Los Gatos, Calif., to Washington to be a prospective witness during the death-penalty phase of terrorist Zacarias Moussaoui's trial.

Hoglan's only child, Mark Bingham, died on United Flight 93 when Moussaoui's colleagues crashed the plane into a Pennsylvania field on that infamous Sept. 11. So, the talk-radio callers want to know, why in the world is she prepared to be a witness for the defense?

This came as a bit of a surprise even to Hoglan herself. She has never been an opponent of the death penalty. In fact, she's not sure if Mark would approve of her telling the jury that Moussaoui, who was convicted of helping to plan the Sept. 11 attacks, should be allowed to live.

But as she followed the trial and listened to Moussaoui speak proudly about his wish to kill Americans, she began to have a tug-of-war between what she refers to as her "higher and lower selves."

"My lower self says, 'We ought to fry him,' " Hoglan told me, smiling apologetically, as she does often. "But my higher self says this is a golden opportunity to demonstrate a higher standard of behavior than Moussaoui has shown toward us. We can show that we are a nation of laws and justice and mercy."

She explained this recently when we met at the Saratoga, Calif., public library, where she and I have talked before when she spent so much time there researching airline security lapses. A former flight attendant, Hoglan had channeled her grief into a personal crusade to make planes safer from terrorists.

Since then, she has been on an emotional journey that has led her to think carefully about her own sense of humanity and what it means to be an American. She likes to think that Mark is guiding her through it.

She told me that the death of her charming, adventurous 31-year-old son hits her "like fresh bad news all the time." She thinks often about the first time the families of Flight 93 passengers were allowed to listen to the cockpit voice recording from Sept. 11, and she heard Mark's voice in the final minutes of his life.

Mark was one of the now legendary passengers who fought back against the terrorists. "I keep hearing him yelling, 'In the cockpit! In the cockpit!' We think they were trying to break through the door," she said, her eyes glistening and her face flushed. "If I'd been there, I would've been with Mark, slugging it out and trying to kill those guys with a coffeepot or whatever was there."

Killing is not on her mind anymore. She's looking for a different kind of justice.

But she is completely sympathetic to victims' family members who want Moussaoui to die. And she's not sure what to say when talk-radio hosts ask her why we should spend hundreds of thousands of dollars to keep him in prison for the rest of his life. "As a taxpayer, I don't have a glib answer for that one," she told me, eyes downcast.

It has not been easy for her to be a woman of strong conviction. She had spent an entire career trying to please people. Even now, she speaks in the gentle tone of someone who desperately wants not to offend. But she speaks up.

And if she begins to lose her nerve, she needs only remember her son's courage during his final moments storming that cockpit.