Editor's note: Sherrilyn A. Ifill is a professor at the University of Maryland School of Law and the chairwoman of the U.S. Programs Board of the Open Society Foundations. She is the author of "On the Courthouse Lawn: Confronting the Legacy of Lynching in the Twenty-first Century."
(CNN) -- The hardest part of listening to Trayvon Martin's mother speak about her son's death is hearing the tone of her voice. It bears a heaviness that speaks not just of grief but of resignation.
Sybrina Fulton is living the nightmare that every black mother carries in the back of her mind every day. Her son has been senselessly killed by someone who didn't see her son -- a normal American teenager -- but saw just a black boy and felt threatened. The police know the killer but have not arrested him.
All of the known facts support the likelihood that Martin was pursued and killed by a zealous neighborhood watch captain. But Martin is black, his assailant, George Zimmerman, is white (Hispanic), and the events took place in Florida, which has a strong self-defense law. So rather than quietly grieve, comforted by the assurance that this terrible wrong will be forcefully addressed, Fulton must do what many black mothers have had to do for decades. She must lead the charge to bring the killer to justice. She must hire a lawyer, although her son broke no law. She must appear at rallies and on the radio to keep public pressure on local police who have refused to arrest Zimmerman.
In the early 20th century, the consequences for the kind of relentless determination displayed by Fulton could be deadly. Of the several dozen black women who were lynched in our nation's history, most were killed in retaliation for demanding the arrest of those who murdered their sons or husbands.
We've come a long way since those days. But Fulton still feels the pain of having to defend the honor of her son and justify the significance of his life.
She does not say this. But in her voice we hear the sound of a burden decades old and almost too heavy to bear. In a way, she is walking the rugged path forged so courageously and publicly by Mamie Mae Till more than 50 years ago, who never rested in her search for justice for her slain son, Emmitt.
The fear of Fulton's terrible journey is what motivates so many black mothers to harangue their sons with demands that they call home when they're out, that they take a friend with them and that they watch their backs. We imagine what could happen and try to do our best to keep the nightmare at bay. Our hearts break when we hear the recount of Martin's call to a friend in the minutes before he was killed. He knew Zimmerman was following him. His fear was mixed with a young man's pride: "I'm not gonna run."
Yes, we know about those parents who don't parent, who let their children run wild without supervision. But we also know the truth. And the truth is that most black mothers parent with determination, authority and fear. Especially those mothers who have sons.
The teenage rites of passage that thrill our white counterpoints send fear down a black mother's spine. When your child is old enough to walk to a friend's house in the neighborhood, it can mean the first of many stop-and-frisk encounters with the police. When they turn 18, they can now be arrested and charged as an adult for being in the wrong place at the wrong time. A new driver's license and car opens the door to driving-while-black stops. Just having a flat tire in the road can end with a senseless murder, like the death of Camille and Bill Cosby's son Ennis on the Los Angeles freeway in 1997.
Without question, white mothers lose their sons to murder too, and black mothers who lose their sons and daughters to murder do so more often at the hands of other black men or boys. There is no comfort for any of these mothers; there is just the hope of justice. But when a white neighborhood watch captain with a record of run-ins with the law follows, shoots and kills a black unarmed teenager and no arrest is made, even the cold comfort of justice is denied.
There are too many weeping, grieving mothers in our gun-soaked, violent nation. All that Sybrina Fulton asks for are answers and justice. Every mother of every race should stand with her.
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The opinions expressed in this commentary are solely those of Sherrilyn A. Ifill.