NEW ORLEANS (AP) — A teenager gunned down by police on a bridge after Hurricane Katrina was shot at least three times while lying face down after being fatally wounded by a shotgun blast to the head, a forensic pathologist testified Thursday at the trial of five current or former officers charged in the case.

Dr. Vincent Di Maio’s testimony supports prosecutors’ allegations that New Orleans police shot unarmed, wounded people who posed no threat to officers and who were seeking cover behind a concrete barrier on the Danziger Bridge.

Defense attorneys say the officers were shot at before they returned fire on the bridge, where they had responded to a distress call less than a week after the 2005 storm. But jurors heard earlier that when no weapons were found on any of the victims, police allegedly plotted to plant a gun, fabricate witnesses and falsify reports to make the shootings appeared justified.

Di Maio, a government witness at the federal trial, said 17-year-old James Brissette was shot at least six times by at least three different weapons. He said a shotgun blast to Brissette’s head would have immobilized him before three other shots struck him.

“The most lethal wounds were in the head,” he said. “The others would have been contributory factors in the death.”

Sgt. Kenneth Bowen, one of the five defendants, allegedly fired one of those last three shots with an AK-47 assault rifle. Di Maio said the evidence he reviewed suggests the bullet from Bowen’s gun ricocheted off the barrier before it entered Brissette’s left arm.

Michael Hunter, one of five former officers who has pleaded guilty in the case, has testified he saw Bowen lean over the barrier and randomly spray gunfire at wounded people.

The shotgun blast that pierced the back of Brissette’s head also struck his right buttock, Di Maio testified.

“The blast most likely occurred when he was down or going down,” he said.

Patrick Lane, a firearms expert, testified earlier this week that he matched four spent shells found in a grassy area on the east side of the bridge to a shotgun used by former officer Robert Faulcon.

Di Maio testified that Brissette also was shot in the right thigh, apparently by an M4 assault rifle, while he was on his back with a flexed knee facing the shooter. Sgt. Robert Gisevius allegedly fired an M4 rifle on the bridge, but the gun wasn’t turned over to investigators.

Prosecutors say Faulcon also fatally shot 40-year-old Ronald Madison, a mentally disabled man, in the back with a shotgun as ran from police on the west side of the bridge. Di Maio said Madison died of wounds from a single shotgun blast to the back.

Four people wounded on the east side of the bridge survived the shootings. Di Maio said Jose Holmes, Brissette’s friend, was shot at least three times. Holmes apparently was holding a hand in front of his face in a defensive position when he was wounded by a shotgun blast, Di Maio testified.

Holmes’ aunt, Susan Bartholomew, was shot at least four times, while her husband, Leonard Bartholomew III, and daughter, Lesha Bartholomew, each were shot three times, according to Di Maio.

“I don’t know who pulled the triggers,” he said during cross-examination. “All I can do is talk about the pathology.”

Di Maio said he based his conclusions on autopsy reports, X-rays of the bodies and photos taken at the scene, including one that shows Brissette’s lifeless body face down on the bridge.

Di Maio, a former chief medical examiner for Bexar County, Texas, is now a private consultant who works for both defense attorneys and prosecutors.

Di Maio was the only witness to testify Thursday, nearing the end of the trial’s third week. Prosecutors are expected to finish presenting their case early next week.

The case is one of several Justice Department probes of alleged police misconduct that followed Katrina, which plunged the flooded city into chaos in 2005. Last year, a jury convicted three New Orleans officers in the death of 31-year-old Henry Glover, who was shot by an officer outside a strip mall before a different officer burned his body in a car.

Copyright 2011 The Associated Press.