By now you’ve probably read about or seen the video that shows a North Charleston, South Carolina police officer gun down a fleeing 50-year-old black man named Walter Scott. Scott posed no serious risk to the officer or the public, yet the officer fired eight rounds, hitting Scott four times in the back and one time in the ear. The events have been retold on many websites so I won’t repeat them in this space.

I would, however, like to take issue with Charles C.W. Cooke’s piece over at National Review Online, entitled, “A Camera Will Mean Justice for Walter Scott.” Cooke writes, “Where there are cameras…the playing field is leveled.”

I believe Cooke is being too generous to the American justice system.

Those of us old enough to remember the Los Angeles riots of 1992 also remember what set them off: the acquittal of several LAPD officers charged with the savage beating of motorist Rodney King.

This ABC News clip of the beating is telling.

What I find most interesting, and didn’t recall until I re-watched the clip, is that the infamous LAPD chief Darryl Gates supported the charges against the officers. In the clip, he said, “the officers struck [King] with batons between 53 and 57 times.” The video shows a handful of officers—in the middle of a virtual platoon of 15 or so—swinging batons without mercy or restraint all over King’s body.

And yet they walked free after a jury trial. (Two were later convicted on civil rights charges filed by George H.W. Bush’s Justice Department.)

You might say, “That was as long time ago. America’s changed since then, hasn’t it?”

Cameras have been particularly effective in clearing innocent people of charges of violence against police, but securing a conviction of a police officer is another story entirely.

In Prince George’s County, Maryland, a teen who had been charged with assault for being rushed and pistol-whipped by a police officer had his charges dropped, but the officer was nevertheless acquitted. In Albuquerque, New Mexico, an officer fatally shot a 19-year-old woman with his body camera rendered inoperable but never faced discipline for it. He stayed on the force long enough to be accused of excessive force in another incident in which his camera mysteriously failed to record. Most recently, many of us saw Eric Garner die, but the police officer who used a banned chokehold was never charged, let alone faced a jury.

The mere presence of cameras, though welcomed, is no guarantee of justice.

As I’ve written here before, police practices need to change, and officers must be held administratively and criminally accountable. Investigators and prosecutors must challenge the testimonial blueprint that an officer must repeat to acquit themselves, not accept the rote recitation as gospel. And the wall of silence that protects bad copsmust be destroyed.

Politically powerful law enforcement organizations and unions will resist efforts to make officers more accountable for their actions. These problems are systemic, engrained in police culture, and they have deadly consequences.

I hope the officer who killed Walter Scott is justly tried and convicted in a court of law. But American history shows that even in the face of such clear and convincing evidence, an officer may walk free. We should all be glad Scott’s death was caught on camera, but it is too early to declare a victory for bringing his killer to justice.