NEW ORLEANS — The killer of retired New Orleans Saints star Will Smith was denied a new trial Wednesday by a Louisiana judge, who then heard tearful, sometimes bitter "victim Impact" testimony from Smith's family and friends.

Racquel Smith said her daughter fears the day Cardell Hayes gets out of prison. She said one of their sons is "lost" without his father. And with tears and anger, she lashed out at the man who shot her and killed her husband during a traffic dispute last year.

"All I ask of you is to tell the truth," she said, looking straight at Hayes and accusing him of lying at his December trial, where he said Smith punched him first.

Hayes, 29, faces up to 40 years for manslaughter for killing Smith, and another 20 years for attempted manslaughter for wounding Racquel. Prosecutors want the maximums, served consecutively, for a total of 60 years.

Other witnesses included Racquel's sister, Smith's older sister, an aunt who helped raise Smith, and two friends of Smith's daughter.

"Man, he was special," an emotional coach Sean Payton said, choking up during his lengthy tribute. "Like rare. Not as a player but as a man, a player and a teammate."

Payton disclosed that he had planned for Smith to coach the Saints' defensive line in 2016.

"There's no winners," Payton declared, recalling how he watched Hayes being found guilty. "I hope I never have to speak at one of these again."

Judge Camille Buras will hear defence arguments when the hearing resumes Thursday, and is expected to announce the sentence no later than Friday.

The judge denied Hayes' request for a new trial, rejecting several defence arguments, including one based on the claim of a newly found witness who contradicted trial evidence by saying he heard more than two weapons fired that night.

Michael Burnside lives near the crime scene. He said he's familiar with guns. He testified that he heard "baps" from a smaller weapon, then "booms" from a larger one. "There were four baps before there were eight booms," he said.

Hayes, who killed Smith with repeated shots from his .45-calibre handgun, has insisted that he fired in self-defence, but evidence at trial showed Smith's loaded .9-mm semi-automatic handgun was found unused inside Smith's car.

Wearing a wild mane of hair and a bushy beard, Burnside spoke clearly and confidently but appeared near tears at times and twice let slip a profanity. He acknowledged that he didn't witness the killing, and called himself a "coward" for failing to come forward immediately.

Assistant District Attorney Jason Napoli noted that Burnside — who said he doesn't own a clock or a calendar — couldn't be certain of the time and date of the shooting he heard. In fact, there was another shooting in the same area about 45 minutes before Smith was killed, Napoli said.

Napoli also noted the lack of evidence of any other guns being fired — no shell casings from a second gun, and no witnesses, other than Hayes, who indicated a second gun was involved.

"That man is certifiably insane. It is very apparent," he later told the judge.

"Just because people are different from you, doesn't make them liars," countered defence attorney John Fuller.

Hayes appeared to have caught something of a break at his December trial when a jury decided against second-degree murder, which would have meant mandatory life in prison.

But New Orleans District Attorney Leon Cannizzaro soon made it clear he believes Hayes deserves a 60-year sentence.

The defence has noted the absence of any serious criminal record and has said Hayes, a tow truck business owner and the father of a 6-year-old son, feared for his life when he encountered a drunken, belligerent Smith in the traffic dispute.