George Zimmerman's acquittal in the Trayvon Martin case set off a wave of protest and a tsunami of commentary about its broader meaning.

Cases like Mr. Zimmerman's naturally raise questions about the quality of justice because they go to the society's underlying tensions, especially when race is involved.

Mr. Zimmerman, 29, who is white, shot and killed the unarmed black teenager inside a gated townhouse community on Feb. 12, 2012. Mr. Zimmerman was a member of a neighborhood watch group and the 17-year-old was staying in one of the townhouses.

Despite the attention that such cases draw, they usually are poor bellwethers of broader social conditions or trends.

In court, the objective of each side is to win. Such trials aren't philosophical debates in search of objective truth. Lawyers for each side try to cast the known facts in the light most favorable to their position so that the bottom-line truth often becomes obscured.

Jury selection itself is a social science. Prospective jurors don't wrap themselves in bubble wrap in their daily lives; they have personal views based on experience. Lawyers strive to find people whose underlying views can best help their cause, and to exclude people whose histories indicate otherwise. When a jury itself is not representative of the population as a whole, its decisions can't legitimately be grafted onto the society as a whole. In this case, the jury of six women - five white and one black - hardly was representative of the community.

There was no doubt how the victim died, but over three weeks the jury heard wildly divergent accounts of how the shooting came to pass. A different jury might well have drawn different conclusions. The system is imperfect, but it's the best one available.

People are free to disagree about the accuracy of the verdict, but the variables within the criminal court system make it a mistake to pose it as anything but the finding in this particular case alone.