When Myrlie Evers was told in 1989 that new information in her late husband’s decades-old murder case was unlikely to move the gears of justice, she did not react in anger.

Instead, the widow of slain civil rights movement hero Medgar Evers listened carefully as Mississippi prosecutor Bobby DeLaughter explained that the state couldn’t find any of the evidence from a past prosecution. Then, she calmly asked his team “Just try."

Faced with the overwhelming odds of a case with few surviving jurors, a defiant defendant who had always maintained his innocence, and a public that had long since seemed to move on from the tragedy, others might have backed down. Instead, Myrlie Evers fought to have the murder case reopened—a battle she had waged for nearly 30 years.

Even before her husband’s 1963 assassination, Myrlie Evers had struggled with the consequences of her husband’s attempts to overturn Jim Crow segregation. As he agitated on behalf of voting rights and against laws and attitudes that pushed black Southerners out of public schools, universities, beaches and fairgrounds, he had sustained multiple death threats and an attempt to bomb his home with a Molotov cocktail. The danger was so severe that Medgar was under FBI protection, and the Evers family had drilled their children on how to respond if shooters ever threatened him at home.

On the night of June 12, 1963, the dreaded happened. Shots rang out in front of the Evers's home. As the kids crawled on the floor to a bedroom, Myrlie went to the front door. Medgar was lying there in a pool of blood, dying from a gunshot wound.

A suspect immediately emerged. A sniper rifle left on the scene of the crime was traced to Byron de La Beckwith, a rabid segregationist who belonged to the White Citizens Council and was known to hate black people. The FBI also traced the sight that the killer had used to Beckwith.

Beckwith was arrested about a week after the murder, but his prosecution was flawed from the start. During jury selection, the district attorney asked every potential juror if he believed it was a crime to “kill a n----” in Mississippi. Only seven black men were included in the jury pool, and none were called to serve.

The all-male, all-white jury heard multiple arguments that Beckwith could not have murdered Evers, including an elaborate alibi and claims that three men, not one, carried out the murder. They saw Ross Barnett, the segregationist sitting governor of Mississippi, go to the defense’s table during the course of the trial, even shaking Beckwith’s hand and clapping him on the back. And they came back with a deadlock that gave Beckwith an automatic mistrial.

A second trial, during which the Ku Klux Klan packed the gallery and burned crosses around Jackson, resulted in the same verdict. A third trial was planned but never carried out, and the trials were eventually dismissed.

The state of Mississippi seemed uninterested in pursuing justice. But Myrlie Evers later told a New York Times reporter that in the days following her husband’s murder, she promised herself, “I'm going to make whoever did this pay.”

In the meantime, Myrlie poured her anger into the civil rights causes Medgar had championed. “More than any of the other civil rights widows,” wrote Krissah Thompson for the Washington Post, “Myrlie Evers showed America her rage.” Over the years, she ran for Congress, remarried and left Mississippi. But whenever she came back, she asked what had been done to put Beckwith behind bars and pressed officials to keep looking for new evidence.

Then, in 1989, she spoke to Jerry Mitchell, a Jackson newspaper reporter who told her he had found evidence that the Mississippi Sovereignty Commission, a state agency that had secretly been given authority to investigate and intimidate civil rights movement leaders, had surveilled Medgar and conducted secret background checks on jurors. When the news broke, she asked the state prosecutor to reopen the case. Despite a missing murder weapon, legal uncertainty about whether Beckwith could be tried again so many years after the crime, and a case file just three pages long, he did.

Then more evidence emerged. When Mitchell questioned the police officers who had provided Beckwith’s alibi, they named different times than they had years before. And even after prosecutors failed to find evidence of jury tampering in the original case, they located new witnesses, thanks to Myrlie’s urging. New witnesses can become difficult to locate the older a case becomes. But in the case of Medgar’s murder, the passage of time allowed some with once-unknown details about his murder to feel safer coming forward than they had in the 1960s.

In 1994, Beckwith finally stood for his third trial. Still defiant, he came to court every day wearing a Confederate flag pin. This time, the jury was more racially diverse—and this time they agreed on a different verdict. When the guilty verdict was read, Myrlie Evers-Williams wept. Afterward, reported the Los Angeles Times, she jumped for joy, then looked up to the sky, saying “Medgar, I’ve gone the last mile of the way.”