This contradicts testimony by a police sergeant that the victim had turned toward officers and was reaching into his waistband when shot.
"Clearly he was shot from behind," said famed New York pathologist Dr. Michael Baden, who examined the body for the family's lawyer.
A prosecutor said the case will go before a grand jury soon and acknowledged the investigation includes the possibility of police wrong-doing.
Ronald Madison, 40, was mentally disabled and lived at home with his mother. He had no criminal record. He was shot when police responded to a report of gunfire on a bridge over the flooded Industrial Canal on Sunday, September 4, six days after Katrina hit New Orleans last year.
It was a week of dire flooding, rampant looting, death by drowning. Police were strained, beset by suicides and desertion. Four people were killed in confrontations with police that weekend alone.
Madison's older brother, Lance, said he and Ronald were walking across the Danziger bridge toward another brother's dental office when teen-agers ran up behind him and opened fire that Sunday morning.
By his account, he and Ronald were running away toward the crest of the bridge when a police team, responding to the report of gunshots, arrived in a rental truck and opened fire on people on the bridge.
Police Superintendent Warren Riley told CNN, "Several of the people were shot and two were killed by our officers in a running gun battle... Most police shoot-outs last somewhere between six and twelve seconds, and it's over with. This was a running gun battle that went on several minutes."
One teen-ager, still unidentified, was killed near the base of the bridge. Another was critically wounded. Three other people with them were also shot and were hospitalized.
Lance Madison said a policeman pointed a rifle at Ronald and shot him as the two of them were running up the bridge. Lance said he helped carry his wounded brother to a motel on the other side of the canal and left him there as Lance kept running to seek help.
The Police Department said in a press release last fall that Ronald Madison, whom it called a second unidentified gunman, "was confronted by a New Orleans Police Officer. The suspect reached into his waist and turned toward the officer who fired one shot fatally wounding him."
Testifying in a preliminary hearing last fall, Police Sgt. Arthur Kaufman said much the same thing: "One subject turned, reached in his waistband, turned on the officers."
Autopsy results, made available to CNN by a source involved in the investigation, directly contradict that police account.
The findings list five separate gunshot wounds in Ronald Madison's back. Three went through the body and exited in front. There were two other wounds in his right shoulder. None of the shots entered his body from the front.
CNN had sued the coroner of Orleans Parish to try to get official access to the autopsy report. At a court hearing on that lawsuit in New Orleans a week ago, the coroner, Dr. Frank Minyard, verified the handwritten autopsy report obtained elsewhere by CNN was indeed prepared in his office by a pathologist on his staff who listed the wounds in the victim's right back.
Under cross-examination by a CNN lawyer, Dr. Minyard testified those five wounds in the back "were entrance wounds, yes."
Dr. Michael Baden, chief forensic pathologist for the New York State Police, met with CNN in New York City two weeks ago to discuss his own observations when he examined Ronald Madison's body for the family lawyer last fall. Asked if Ronald could have been facing the police when shot, Dr. Baden said, "Absolutely not."
No weapon was found on or near Ronald Madison's body.
Assistant District Attorney Dustin Davis, testifying in the same court hearing on the CNN lawsuit, said a grand jury has been assigned to investigate the Danziger Bridge shootings. However, the grand jury has not yet met on the case because the New Orleans Police Department has yet to complete its final report, eight months after those deaths.
The CNN attorney asked Davis, "What you are investigating in that case is whether any of the police officers may be indicted for homicide, is that correct?"
Davis answered, "That's partially correct. We are also looking at Mr. Madison's involvement in the incident."
Lance Madison was arrested on the other side of the bridge where his brother was killed and was accused of shooting at the police officers in the gun battle. He, too, had no weapon when taken into custody. He was released from jail after six months because the District Attorney's office had not initiated any prosecution, although the investigation remains pending.
Sgt. Kaufman testified at the bail hearing for Lance Madison last fall that another policeman saw Lance throw a gun into the Industrial Canal as he was going over the bridge. Lance Madison denies that. He told CNN correspondent Drew Griffin, "I had no gun, at all." Asked if Ronald had a gun, Lance answered, "No, he didn't."
In a CNN interview earlier this month, Griffin told Police Chief Warren Riley, "We understand Ronald Madison was shot in the back five times."
Riley said, "Those are things I can't comment on and no one can comment on until the investigation is concluded."
Griffin asked Riley if he was concerned about his officers' actions and Riley replied, "Certainly, we do not condone our officers overreacting, even in the most chaotic time," but he went on, "We don't know that they overreacted. From the radio transmission, it sounds like their lives were in danger."
Riley turned down a request by CNN to interview the officers who were involved.
A 25-year career employee at Federal Express, Lance Madison has no criminal record.
At the end of the CNN interview, Riley conceded the two Madison brothers may not have been connected with the other people on the bridge that day.
"I don't know if those young men were innocent or not. I really don't know if they were with that group or not," Riley said. "I really don't know."