Ariston Waiters was shot and killed almost four years ago, more than long enough for his death at the hands of a Union City police officer to fade into obscurity. That’s particularly true given that the case had been presented three years ago to a Fulton County grand jury, which heard the available evidence and declined to indict, accepting the officer’s claim of self-defense.

Just another tragic story in the big city.

Earlier this week, though, the Waiters case was reopened by the Fulton County District Attorney. Part of that has to do with the basic facts of the case, which remain troubling even after all this time. Waiters, 19, had been unarmed and was apparently guilty of nothing more than running away from police who had arrived to break up a fight. Yet somehow, after he ceased fleeing, Waiters was shot twice, in the back, while he lay on the ground.

Furthermore, a new investigation by The Atlanta Journal-Constitution and Channel Two Action News has uncovered potentially crucial information that the grand jury was not allowed to hear.

For example, there is evidence that the personnel file of the officer involved may have been cleansed of potentially troubling information by Union City officials before it was turned over to the district attorney’s office. In addition, the grand jury somehow never heard testimony from a Union City police supervisor, Lt. Chris McElroy, who warned investigators at the time that the officer who shot Waiters had changed his story significantly.

That officer, Luther Lewis, allegedly told McElroy nothing about Waiters trying to grab his police firearm, which proved crucial in his self-defense narrative. According to McElroy, that crucial addition came after Lewis had a private discussion about the case with Union City Police Chief Chuck Odum.

We should also acknowledge two other points:

1.) A changed national environment contributed to the reopening of the Waiters case. Videos documenting what appear to be clear cases of police misconduct have given new credibility to allegations that police have at times been too eager to resort to deadly force, either out of gross incompetence or callous disregard for the lives of those in their custody.

2.) Given the ready availability of firearms, police officers have every cause to be wary, as the bizarre biker shootout in Texas over the weekend demonstrated. In many if not most cases of police shootings, evidence demonstrates that officers have had little or no choice but to shoot to protect their own lives or those of others.

The question is, how do you distinguish between a justified police shooting and an unjustified shooting? And who should be entrusted to make such a judgment? Victims of such shootings, particularly in minority communities, have long argued that law enforcement agencies are more interested in protecting themselves from scrutiny than in pursuing the truth.

The allegations in the Waiters death reflect the problem perfectly. If proved in a court of law, they constitute a conspiracy by law enforcement itself to cover up what really happened on the evening of Dec. 14, 2011. And that’s the heart of the mistrust that continues to degrade trust between law enforcement and those they are sworn to protect.