Diann Aldridge (third from left), the mother of Nykea Aldridge, during a prayer vigil for her daughter. Photograph by Joshua Lott / Getty

On August 26th, at 3:30 in the afternoon, Nykea Aldridge was pushing her month-old daughter in a baby stroller in a neighborhood on Chicago’s South Side when two men began shooting at a man getting out of a car. Some of their bullets missed their target and hit Aldridge in the arm and in the head. Aldridge, who was thirty-two years old and a mother of four, had been walking from a school where she had just registered her older children. She died forty-five minutes later in the hospital. Two things made Aldridge’s death different from most of the five hundred and nine fatal shootings that have occurred so far this year in Chicago: it received national attention because Aldridge’s cousin is the basketball star Dwyane Wade, and within forty-eight hours the police announced that they had arrested two suspects—two brothers—for the murder.

It's the latter difference that may help to make sense of the wave of violence that has overtaken a large swath of the city. While Chicago mourned Aldridge’s death, many also asked: If the police could make an arrest in her murder so quickly, why had so many other murders been left without resolution?

This week, Mayor Rahm Emanuel is scheduled to give a major address on the city’s violence. Over the years, the police have tried various tactics to diminish violence and murder, including community policing, targeting high-crime areas called “hot spots,” starting specialized anti-gang units, and, most recently, employing algorithms to predict who is most likely to pick up a gun and shoot someone. Nothing has seemed to work. In the first eight months of this year, murders have been up an unprecedented fifty per cent. The situation has become so severe that, earlier this month, one alderman proposed that all police be required to carry military-quality first-aid gear. But one issue is rarely raised: year after year, the vast majority of murders and non-fatal shootings in Chicago go unsolved. Last year, the police charged individuals in just twenty-six per cent of all murders. Of the nearly three thousand non-fatal shootings, only ten per cent of the assailants were charged, which means that you have a pretty good chance of shooting someone in Chicago and getting away with it.

This failure to find and charge perpetrators could be contributing indirectly to violence. A case is considered cleared when someone has been identified and charged, or if the suspect dies before charges have been filed. Chicago’s homicide-clearance rate is less than half the national average of sixty-four per cent. Thomas Hargrove, a former newspaper reporter who now runs the Murder Accountability Project, an organization that examines murder-clearance rates, said that there is a clear correlation between catching criminals and the murder rate itself. In cities where the clearance rate is better than average, the murder rate is 9.6 per hundred thousand. Among cities where the clearance rate is lower than average, the murder rate is nearly twice that. “If you allow murders to go unsolved, it all goes to hell,” he said. In 2015, Chicago’s murder rate was 17.8 per hundred thousand.

The Chicago Police Department blames the low clearance rate principally on the lack of coöperation from witnesses. At a press conference announcing the arrests in Aldridge’s murder, the police superintendent Eddie Johnson drew attention to this belief when he said, “You know why we captured them right away? Because the community helped us with it.”

While it’s true that many people in the city’s mostly poor African-American neighborhoods are reluctant to coöperate with the police, the reasons are complicated. In reporting a book about the city’s violence, I’ve come to believe the so-called no-snitch culture is misunderstood. Most victims and witnesses stay quiet because they’re afraid of retaliation by friends of the shooter, not because of some unwritten code of the streets. One woman I interviewed has a job supporting victims who have been asked to testify in criminal cases, and yet when her teen-age son was shot five times she urged him not to work with the police. She worried that he’d be shot again if he did. “Sometimes,” she told me, “I go home feeling guilty” for urging victims to testify.

The fear is well founded. I came to know the family of Ramaine Hill, a young man who agreed to identify the assailant who shot him—and to testify in court. His willingness to talk to the police helped resolve the case; the shooter pleaded guilty and was sentenced to fifteen years in prison. In the course of the next year, however, Ramaine was pressured and threatened so that he would reverse his testimony. On September 1, 2013, as he walked through a public park on his way to work, at a supermarket, someone walked up and shot him in the head. There were witnesses to the murder, but, three years later, no one has been willing to step forward. He was willing to testify, Ramaine's aunt, Joyce Taybron, who raised him, told me, “and look where he’s at. He got killed.” His murderer has never been charged.

The inability of the police to solve crimes, coupled with a spate of incidents caught on video in which police are seen shooting unarmed individuals, has hardened what many African-Americans already believed: that justice is hard to come by. For some, distrust has turned to contempt. On the same day that Aldridge was shot to death, police responded to a shooting of a twenty-two-year-old man on a street in Englewood, a neighborhood on the city’s South Side. As they secured the area with yellow police tape, they were confronted by a dozen or so young men. People often get agitated at crime scenes, but these young men became belligerent, taunting and swearing at the police. They seemed defiant, waving cell phones in the faces of seven uniformed officers. “Get the fuck off my block,” one of the young men yelled. Another sneered at a black officer: “You’re a traitor. You’re a traitor. You’re bogus as hell.” Nearby, someone shot a gun three times, and as officers ran in the direction of the gunfire, one young man yelled, “Run, bitch, run.” The scene was described and filmed by the Chicago Tribune. At one point, one of the young men threw a pink cupcake on the ground and dared an officer to “eat it.” In the end, the police arrested the twenty-two-year-old man who had been shot in the ankle, and charged him with attempted first-degree murder. The police allege he’d been in a firefight. The other shooter, whom the police have not yet identified, has not been caught.

The police department has acknowledged the need to repair its relationship with the African-American and Latino communities, but its efforts have felt clumsy at times, and sometimes dismissive of the very people they’re trying to reach. In recent years, the department has tried to pierce the gangs by employing something it refer to as “call-ins.” These call-ins have two components: they let people who have been in trouble with the law know that if someone was killed in their community, the police would come after their entire gang; and they offer help finding a job. I attended one of these events, which was held on the second floor of a church building, and saw young men just out of prison, their heads held low, berated by police officers and prosecutors for their past behavior. The part where they were supposed to get help finding a job seemed an afterthought, and only a couple of the men stayed to meet the representative from a local social-services agency. The experience had been humiliating and they were eager to move on.