Mamie Till-Mobley, 81, who wanted the world to see her teenage son's disfigured face after his slaying in Mississippi in 1955 and who became a figure in the civil rights movement, died of a heart ailment Jan. 6 at a hospital in Chicago. She had kidney failure.

The murder of 14-year-old Emmett Till and an all-white jury's decision to exonerate the two white defendants -- after about an hour of deliberations -- was considered a defining moment in the growing civil rights movement.

The teenager, who was said to have breeched a social wall by whistling or otherwise communicating with a white woman without proper deference, became a martyred symbol of the growing movement. Months later, Rosa Parks and the Montgomery, Ala., bus boycott further strengthened the movement.

Mrs. Till-Mobley continued to speak out about her son, but many black leaders felt her greatest role came at the height of her pain: the decision to have an open coffin.

The press took pictures of Till with a bullet in the skull, an eye gouged out and his head partially crushed. His body had been found floating in the Tallahatchie River, identifiable only by the ring Till wore that belonged to his late father.

"She was a very articulate teacher who saw the pain of her son and did a profound, strategic thing," Jesse L. Jackson told reporters. "When they pulled his water-soaked body from the river, most people would have kept the casket closed. She kept it open."

In summer 1955, Mrs. Till-Mobley sent her son from their Chicago home to stay with relatives near Money, Miss. Although she had reared him to believe that skin color made no difference in a person's worth, she also had warned him that the reality was far different in the Deep South during that era.

The details of Aug. 24, 1955, are still in dispute. In one account, Till bragged of a white girlfriend in Chicago, prompting friends to dare him to talk to the white wife of a store owner in Money. Some said he whistled at her, others said he said, "Bye, baby," on his way out of the store.

Mrs. Till-Mobley said her son had a stutter and often had to whistle to make certain sounds.

The white woman's husband, Roy Bryant, was enraged. He and his half brother, J.W. Milam, found Till at a shack, where he was staying with relatives, and led him away at gunpoint.

Later, Bryant and Milam said they beat Till but left him alive. The jury found them not guilty, the case was not reopened and the two men later died.

Mamie Elizabeth Carthan was born in Hazelhurst, Miss., and grew up in Chicago. She was a 1956 cum laude graduate of Chicago Teachers College and in 1975 received a master's degree in administration and supervision from Loyola University in Chicago.

She taught special education in Chicago elementary schools. In recent years, she worked with writer Christopher Benson on a book about her son, "The Death of Innocence," scheduled to be published this fall by Random House.

"People have told me to let this thing die, even people in my own family," she told the Associated Press last month. "But people need to be aware."

Her husband and Emmett's father, Louis Till, died in the mid-1940s. Her marriage to Lemorris Bradley ended in divorce.

Her third husband, Gennie "Gene" Mobley Jr., whom she married in 1957, died in 2000.

Survivors include two stepdaughters; six grandchildren; and eight great-grandchildren.