The homicide rate soared last year at a speed unseen since 1968, shows FBI data released on Sept. 26.

Almost 15,700 people fell victim to homicide in 2015, an increase of more than 10 percent (1,532 homicides) over the year before.

Fifteen cities were responsible for almost 40 percent of the increase, most notably Baltimore (133 more homicides), Chicago (67 more), Houston (61 more), Washington (57 more), and Milwaukee (55 more).

But even excluding these 15 cities, the homicide rate increased by more than 6 percent - a spike unseen for decades.

Despite the increase, the rate is still lower than in 2009 and many decades prior to that. The last era of homicide rates below 5 per 100,000 ended in 1964.

It may be too early to judge what the 2015 spike means, but experts suggest a slowdown in policing and damaged community relations could be factors.

Homicide rate per 100,000 inhabitants in the U.S., 1950-2015. (Sources: FBI Uniform Crime Reporting, infoplease.com, and disastercenter.com)

Major Cities

In 2016, homicide rates started to decrease in some cities, but worsened in many others. In Milwaukee, for example, homicides fell 26 percent in the first half of 2016 compared to the first half of 2015, according to data released by the Major Cities Chiefs Association.

But for Chicago, the worst was yet to come. During the first weekend in October, five people were shot dead in the city. The year’s total as of Oct. 4 is 548 murders, according to a tally by DNAinfo. That’s already 70 more homicides than in all of 2015.

The situation in Chicago is linked to the outrage sparked by the 2014 police shooting of Laquan McDonald, a black teen carrying a knife, according to David Kennedy, professor at John Jay College of Criminal Justice and director of the National Network for Safe Communities.

Similarly, he linked the situation in Baltimore to the 2015 death of Freddie Gray in police custody.

Kennedy said minority communities saw the deaths as egregious police misconduct in places where relationships with police “were already deeply, deeply strained and damaged.”

And damage to the legitimacy of police leads to more crime, Kennedy said.

“There’s very solid research, as well as a whole bunch of practical, everyday experience, that says that when the communities’ perception of legitimacy [of law enforcement] goes up, violent crime goes down. And when legitimacy goes down, violent crime goes up,” he said.

Citizens might stop calling the police to report a crime, or if they do talk to police, they may fear backlash from the community. Criminals then gain confidence that nobody will call the police on them or help police catch them.

For example, after the 2004 beating of Frank Jude by off-duty Milwaukee police officers, citizen crime reporting to 911 dropped by about 20 percent for a year, a recent Harvard University-sponsored study found. The drop was larger and lasted longer in predominantly black neighborhoods. In the six months after Jude’s beating, homicides in Milwaukee spiked by more than 30 percent. They subsided again in the same six months the following year.

It’s hard to say how much this phenomenon affects homicide rates nationally, but it’s likely to be hurting more cities than just Chicago, Baltimore, and Milwaukee.

“Those same trust and legitimacy dynamics could absolutely be in action elsewhere,” Kennedy said in an email.

Policing Slowdown

It’s not that police officers are not doing their jobs, said Heather Mac Donald, a fellow at the Manhattan Institute, a conservative think tank.

She believes officers may be hesitant to police too proactively, especially in minority communities, for fear of being accused of racial profiling.

FBI Director James Comey has a similar view.<

“There’s a perception that police are less likely to do the marginal additional policing that suppresses crime, the getting out of your car at two in the morning and saying to a group of guys, ‘What are you doing here?'” Comey said at a press conference in May.

In Chicago, for example, discretionary police stops have decreased 82 percent since the beginning of 2016. The decrease started last year.

In Baltimore, the “on-view” arrests - the ones officers make without a warrant when they see a crime - have dropped “drastically,” according to Andrew Hoverman, a criminal defense attorney in Maryland who serves as a court-appointed attorney in Baltimore.

He couldn’t quantify the drop for the whole city, but said other Baltimore public defenders have mentioned the same issue.

And fewer people are going through the court system. Hoverman said that after Freddie Gray’s death, there have been so few arrests that the court laid off some public defenders and those remaining still have had less to do.

Paradoxically, Chicago and Baltimore both reported a 30 to 40 percent increase in gun seizures for the first half of 2016.

Turning the Tide

Kennedy said police need to do two things to salvage the situation: One, focus efforts on putting the worst and most notoriously violent criminals behind bars, and two, restore or create trust and legitimacy within communities.

Legitimacy, he said, “is driven by the public’s belief that the police are acting fairly and in the community’s best interest, are not acting out of prejudice or bias or racism, care about what the community thinks, and give the community a chance to express it.”

Kennedy’s points are similar to the concepts of precision policing and neighborhood policing propagated by the just-departed New York City Police Commissioner Bill Bratton.

This tactic, however, may not work everywhere, according to Melissa Hamilton, a visiting criminal law scholar at the University of Houston and a former police and corrections officer.

She recommends a similar approach - focusing on crime hot spots and improving community relations - but said it has to be tailored to each locale. Police can’t just take whatever worked elsewhere, she said. They need to figure out how to connect with their particular communities.

It may be especially challenging to rebuild the connection between police and minority communities in cities like Chicago. As Kennedy noted, if they never had a positive relationship to begin with, the police would have to start from scratch.