The man accused of fatally shooting CFL player Joe McKnight formally pleaded not guilty Monday to a second-degree murder charge.

Ronald Gasser, 55, of Terrytown, had initially been arrested on a manslaughter charge following McKnight's Dec. 1 death. Last week, he was indicted on a second-degree murder charge, which carries a mandatory life sentence. He's jailed on US$750,000 bond.

"It was a case of justifiable homicide," defence attorney Gerard Archer told reporters after a brief arraignment hearing at the Jefferson Parish Courthouse in the New Orleans suburb of Gretna.

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Authorities have said the 28-year-old McKnight, who was black, and Gasser, who is white, were driving erratically and yelling at each other prior to the shooting. The confrontation took place as they were travelling over the Mississippi River on a heavily travelled bridge that links downtown New Orleans to its west bank and adjoining suburbs in neighbouring Jefferson Parish.

Authorities said the shooting happened after both cars had stopped and McKnight approached Gasser's vehicle. Gasser shot McKnight three times.

Last week, Archer and co-defence counsel Matthew Goetz said they believe McKnight tried to enter Gasser's car through the passenger window. They noted that Gasser stayed on the scene after the shooting and said he co-operated with police. They said that Gasser did not know McKnight and said the shooting was not racially motivated.

McKnight, who played for the Edmonton Eskimos and Saskatchewan Roughriders last season, was considered the No. 1 running back recruit in the United States when he came out of John Curtis Christian School in Louisiana in 2006.

He signed with the University of Southern California, where he ran for 2,213 yards and 13 touchdowns and caught 66 passes for 542 yards and two scores in three seasons. In the NFL, he played three seasons for the New York Jets and one with the Kansas City Chiefs.