The following editorial first appeared in The Wall Street Journal on July 15, 2013:

An American criminal defendant is presumed to be innocent until proven guilty beyond a reasonable doubt, and that's the standard to keep in mind when considering the jury's not guilty verdict Saturday for George Zimmerman in the murder of 17-year-old Trayvon Martin.

The case has been fraught with racial politics from the start, but inside the Sanford, Florida courtroom, the jurors had to wrestle with the standard that is a hallmark of American justice. No one but Mr. Zimmerman knows what happened that early evening in 2012 when he followed Martin, an unfamiliar young, African-American male visiting the neighborhood. A scuffle ensued, Zimmerman shot Martin in what he says was self-defense, and prosecutors never produced an eyewitness or even much evidence to disprove Mr. Zimmerman.

The verdict compounds the tragedy for the Martin family, but no one can claim that their son was not represented in court. The state threw everything it had at Mr. Zimmerman. Gov. Rick Scott replaced local prosecutors with a special team from Jacksonville, the judge often ruled favorably for the prosecution, including the addition of the lesser manslaughter charge (in addition to second-degree murder) at the end of the trial.

Still the state could not prove its case to the satisfaction of the six jurors, all women, for whom the easiest decision in terms of public approval would have been to convict. No less than President Obama had commented on the local case after Mr. Zimmerman was not originally charged by local authorities.

"If I had a son, he'd look like Trayvon," Mr. Obama said. He was echoed by hundreds of politicians and commentators who wanted to put racial profiling on trial as much as they did Mr. Zimmerman. But a criminal trial is not a legislature, or a venue to debate social policy.

Benjamin Jealous of the NAACP is already lobbying Attorney General Eric Holder to indict Mr. Zimmerman on federal civil-rights charges. To do so and win a conviction would require proof that Mr. Zimmerman was motivated by racial animus when the record shows little more than a reference by Mr. Zimmerman to "punks" in a comment to a police dispatcher.

Millions of Americans would see such federal charges as an example of double jeopardy, and a politicized prosecution to boot. In this context, it was good to see Mr. Obama's statement Sunday that "we are a nation of laws, and a jury has spoken."

The larger issue of how American society, and especially the police, treat young black males deserves attention and often receives it. There is no doubt that many law-abiding black men are eyed suspiciously in some quarters because they are black. The motivation may sometimes be racial. But such a discussion also cannot exclude that the main victims of crimes committed by young black men are other blacks. A policy like New York City's "stop and frisk" rule prevents more crime in minority neighborhoods against minorities than it does in white areas of Manhattan.

Mr. Zimmerman made many mistakes that February evening, not least failing to heed police advice not to pursue Martin. Despite his acquittal, he will pay for those mistakes for years as he defends against a possible civil suit and must wear a bullet-proof vest to protect himself from threats of violent revenge that he has to take seriously.

If there is any satisfaction in his acquittal, it is that the jurors followed the law's requirements that every defendant deserves a fair trial, even one who becomes a symbol of our polarized racial politics.