A man has been convicted of homicide by vessel over a jet-ski crash which killed RnB singer Usher's 11-year-old stepson.

A jury in Hall County in the US state of Georgia, also found Jeffrey Hubbard guilty of serious injury by vessel, reckless operation of a vessel, unlawful operation of a personal watercraft and a boat traffic violation.

The crash on Lake Lanier, north-east of Atlanta, in summer 2012, killed Kile Glover and left another teenager seriously injured.

Investigators said the jet-ski Hubbard was riding hit the children as they were being towed on an inner tube. Kile died of head injuries six days later.

Hubbard's lawyers argued that what happened was a tragic accident and was not linked to recklessness.