Eric Garner was allegedly selling cigarettes illegally in Staten Island, N.Y. Michael Brown was jaywalking in the middle of a Ferguson, Mo., street. Now the country is trying to understand how these seemingly trifling offenses led to both black men being killed by white police officers.

Unfortunately, a public airing of the actions and responses that led to their deaths was prevented by prosecutors who decided essentially to try the cases in secret grand jury proceedings that exonerated the officers. Perhaps they would have been found not guilty in open court trials, but we'll never know.

Trials might have revealed whether the officers could have realistically employed alternatives to deadly force. A trial might have revealed why Ferguson Officer Darren Wilson didn't wait for backup before confronting Brown, or why he couldn't use pepper spray or a Taser instead of shooting the man.

A trial might have revealed why at least five Staten Island police officers felt they had to drag Garner to the ground while one placed what appeared to be a stranglehold on his throat, prompting the man's last words, "I can't breathe." A coroner ruled Garner's death a homicide. A trial would have revealed why no one was convicted of a crime.

Grand juries are supposed to decide whether a trial should occur. A trial jury then decides guilt or innocence. That the prosecutors in Missouri and New York seemed to go out of their way to avoid open trials in which all the evidence is aired has left the impression that they had ulterior motives.

Prosecutors can have conflicts of interest. They work closely with police and rely on officers to help build their cases. Elected district attorneys also rely on police for political support. So it may make sense to appoint special prosecutors in deadly-force cases. It also makes sense that the Justice Department's Civil Rights Division is conducting its own investigations of the deaths of Garner and Brown.

Beyond that, the hard work to build better relationships between police and the minority communities they serve must occur. Toward that goal, President Obama has appointed a task force that includes Philadelphia Police Commissioner Charles Ramsey. Here's hoping their work can ease the tension that for weeks has made it harder for all of us to breathe.