The St. Louis County grand jury’s decision not to indict the white police officer who in August shot and killed Michael Brown, an unarmed black teenager, would have generated widespread anger and disappointment in any case. But the county prosecutor, Robert McCulloch, who is widely viewed in the minority community as being in the pockets of the police, made matters infinitely worse by handling this sensitive investigation in the worst possible way.

First, he refused to step aside in favor of a special prosecutor who could have been appointed by Gov. Jay Nixon of Missouri. He further undermined public confidence by taking a highly unorthodox approach to the grand jury proceeding. Instead of conducting an investigation and then presenting the case and a recommendation of charges to the grand jury, his office shifted its job to the grand jury. It made no recommendation on whether to indict the officer, Darren Wilson, but left it to the jurors to wade through masses of evidence to determine whether there was probable cause to file charges against Officer Wilson for Mr. Brown’s killing.

Under ordinary circumstances, grand jury hearings can be concluded within days. The proceeding in this case lasted an astonishing three months. And since grand jury proceedings are held in secret, the drawn-out process fanned suspicions that Mr. McCulloch was deliberately carrying on a trial out of public view, for the express purpose of exonerating Officer Wilson.

If all this weren’t bad enough, Mr. McCulloch took a reckless approach to announcing the grand jury’s finding. After delaying the announcement all day, he finally made it late in the evening, when darkness had placed law enforcement agencies at a serious disadvantage as they tried to control the angry crowds that had been drawn into the streets by news that the verdict was coming. Mr. McCulloch’s announcement sounded more like a defense of Officer Wilson than a neutral summary of the facts that had led the grand jury to its conclusion.