D.C. Police Chief Cathy L. Lanier and Mayor Muriel E. Bowser on May 21. (Win Mcnamee/Getty Images)

On Wednesday afternoon, D.C. Mayor Muriel E. Bowser (D) and Police Chief Cathy L. Lanier announced with fanfare the closing of a June 23 homicide case in which the victim was found dead in a burning trash bin.

One unsolved murder down, countless more to go.

On July 4, 2014, James Oh was physically assaulted by two male teens wearing hooded sweatshirts and masks during an armed robbery at his store three blocks from my home. Oh died of his injuries on July 8, 2014. I devoted a column to the crime, which was caught on tape by the store’s surveillance camera.

On June 6, I wrote about journalist Charnice Milton, who was gunned down on the evening of May 27 in Southeast .

And then there was my February column about 19-year-old Navontae Howard, also fatally shot in Southeast.

The deaths of Oh, Milton and Howard have another common and unsettling feature: Their killers are at large.

Homicides in the District are up 17.7 percent over this time last year, with 73 slayings as of Thursday.

Worse, people are getting away with murder.

So far this year, 48 D.C. homicides have gone unsolved. The killers of 70 homicide victims in 2014 have not been arrested. Fifty-four homicide cases from 2013 remain unsolved.

This scourge of unsolved murders has been building over the years.

In 2012, The Post’s Cheryl W. Thompson reported that a review of nearly 2,300 slayings between 2000 and 2011 found that “less than a third” had led to a conviction for murder or manslaughter. As of that October, she reported, more than 1,000 homicide cases in our nation’s capital were unsolved.

Think about it.

All those killers: riding the subway, filling the gas tank, standing at the curb, sitting on the bus, behind the wheel. Free as birds. As families, without justice, grieve.

And it’s been going on for a long time. An earlier Post study, in 1993, found that only 25 percent of the 1,286 homicides between 1988 and 1990 led to a conviction.

Yes, homicides have been declining in recent years. That, however, doesn’t mean more murderers are paying the price. As with the case of the two young men who killed James Oh, and the person who ended Charnice Milton’s life, and the unknown shooter of Navontae Howard, murderers stand a good chance of escaping arrest and prosecution.

This column, I hasten to point out, is not meant as an anti-police screed. Some might contend that police attitudes toward victims affect the time and energy put into solving murder cases, especially “lifestyle” crimes that involve gangs and drugs.

But there’s no credible evidence that Lanier and her officers are slacking off on their investigations. And trial work by prosecutors has improved conviction rates, once cases get to court.

The problem of unsolved homicides involves more than the expertise of the police and the investigative tools used to handle those cases.

Look at the multiyear photos of the victims on the Metropolitan Police Department Web site. The overwhelming majority are young African American males.

Most pulling the triggers or wielding the knives are believed to be African American males, too.

Unless sensational, like a quadruple murder in an upscale Northwest neighborhood, a prominent reporter’s slaying or a brutal stabbing on a Metro train with eyewitnesses, most murders don’t hit the headlines. Especially those that occur in neighborhoods where everybody knows everybody and the killers aren’t strangers.

That may shed light on the slayings of Oh, Milton and Howard and other unsolved cases.

It’s not that the people who may know something don’t think that the lives of these victims are important. It’s just that they place more value on their own lives, which they consider too important to get labeled “snitch.” Too important to risk becoming a victim of retaliation. Too important to even let on that they know something.

That’s what intimidation and fear of revenge can do to a community, especially one that has seen witness killings in the past.

Ken McClinton, father of slain journalist Milton, said, “This is a city that has closed its eyes to death and a culture of fear.”

Thus conspiracies of deadly silence, even as bodies continue to fall and killers get away.

Comes now the chant: “Black lives matter.”

Perhaps so. But only when whites take black lives?

Is that the only time to come forward?

The answer lies in our actions.

Read more from Colbert King’s archive.