Baltimore Police officer Caesar Goodson leaves a courthouse in Baltimore on June 14 during his trial in the death of Freddie Gray. (Bryan Woolston/Reuters)

MANY PEOPLE feel frustrated and angry at the acquittal of a Baltimore police officer who drove the van in which Freddie Gray suffered a fatal spinal injury. Another black man unnecessarily dead at the hands of police; another case with no one held accountable. The fact that evidence at least was aired and carefully weighed in an open court of law offers some consolation — but not enough. Now it is more essential than ever to ensure that lessons are learned from the tragic case and procedures changed, even if no one is held criminally responsible.

Citing “insufficient evidence,” Judge Barry G. Williams on Thursday found Officer Caesar R. Goodson Jr. not guilty of all charges in the April 2015 death of Gray. The death of the 25-year-old man, who had been arrested after essentially looking the wrong way at police and fleeing, sparked days of violent protest in Baltimore. Of six officers charged, Mr. Goodson faced the most serious charges, and his acquittal marks the third time that prosecutors failed to secure a conviction. The trial of one officer ended in a hung jury, and another officer was acquitted last month, also by Judge Williams.

Those results have caused some to double down on criticism of Baltimore State’s Attorney Marilyn Mosby for bringing the charges in the first place. They say she acted in haste for political reasons of trying to quell the turmoil that engulfed the city. To be sure, fault can be found with some of the office’s actions — particularly with some questionable conduct during Mr. Goodson’s trial — and Ms. Mosby would do well to determine if there are weaknesses in her office that should be addressed. Why weren’t prosecutors able to prove the charges beyond a reasonable doubt? That, though, is not meant to second-guess her decision to bring charges. Prosecuting police officers is always difficult and, as former state senator Clarence M. Mitchell IV pointed out, it showed “courage to bring charges when it appeared that the police had done something wrong.” And it is clear from the $6.4 million the city paid to settle the civil suit brought in Gray’s death that police bear responsibility for his death.

Gray’s death also made clear the long-standing problems with Baltimore police and what many African American residents see as a pattern of harassment and excessive force in their neighborhoods. The Justice Department has an ongoing investigation into the police department’s practices that hopefully will result in bringing about changes that can help prevent other people from being treated as callously as Gray was.