The New Orleans police officers accused of killing two unarmed citizens on Danziger Bridge in the chaos that ensued after Hurricane Katrina and plotting to cover it up pleaded not guilty before a federal judge Wednesday.

A tentative trail date of Sept. 13 has been set in the prosecution of former officer Robert Faulcon, Sgt. Robert Gisevius, Sgt. Kenneth Bowen and officer Anthony Villavaso II (pictured in order from left), who proclaimed their innocence. A fourth officer charged in the killings appeared in a Texas court but has not yet entered a plea.

The charges against the four men carry a maximum sentence of the death penalty, but federal prosecutors have not stated whether they will seek it.

Even though the idea that uniformed officers could shoot innocent civilians seems absurd, the officers' defense will have a tough time if it chooses to fight the case through a trial.

Five former officers have already pleaded guilty to helping to cover up the shootings, so their testimony will be key. These ex-cops told investigators that officers made up witnesses and reports and even sought to plant a gun on a suspect to make it appear as if the shootings were justified.

With all due respect to the legal concept of presumed innocence, these four officers are toast at least as far as the obstruction of justice charges go.

Having this case go to trial, though, especially with the most serious charges involving the killing of two unarmed civilians, will likely reveal what really happened on the day of the shootings.

The shootings occurred Sept. 4, 2005, just six days after Hurricane Katrina flooded the city, leaving bodies floating and looters in control of city streets.

Police received calls of shootings at Danziger Bridge (pictured below). Seven officers covered the bridge and shot at the first people they saw, according to prosecutors, who added that the victims were simply trying to find food.

Two people were killed and four others were wounded.

According to prosecutors, Faulcon shot Ronald Madison, a mentally disabled man, in the back, with Sgt. Bowen kicking and stomping Madison before he died. And Madison's brother, Lance, was arrested and charged with trying to kill officers and was held in jail for three weeks before being released.

The four charged officers are also accused of shooting at another unarmed party on the bridge, killing 17-year-old James Brissette and wounding four others.

The only good to come out of this terrible investigation of police-sanctioned killings is the work of federal investigators, who spent two years building the case. It's clear that a set of outside eyes was needed to examine this case.

Case in point, an earlier internal police investigation found the officers innocent of any wrongdoing in the Danziger Bridge shootings.