The New South Wales Government is seeking to appeal against the sentence for the killer of truck driver Bob Knight.

Attorney-General Greg Smith has called for advice from the Director of Public Prosecutions on the possibility of appealing against the sentence.

On Thursday, Mahmoud Mariam, who was convicted of killing Mr Knight, laughed after he was sentenced to at least five years and nine months in jail.

Mr Knight was shot dead while he was in his truck waiting at traffic lights at Milperra in Sydney's south-west in 2009.

He was hit by a stray bullet fired by Mariam in a dispute with another family in a nearby restaurant carpark.

Premier Barry O'Farrell slammed the penalty, which he said was "clearly inadequate".

"It's the sort of decision that lowers community confidence in the judiciary," he said.

"It's one that I've asked the Attorney-General to provide a report to me as to what, if anything, can be done to ensure that what should be a tougher penalty is imposed."

In sentencing, Justice Megan Latham said the 28-year-old Mariam wore his contempt for the law like a badge of honour.

"The offender was a mature adult who consciously and arrogantly engaged in a mindless display of violence in the presence of much younger men," she said.

"The offender himself has at no stage expressed the slightest remorse for the death of Mr Knight."

Mr Smith is seeking advice on the possibility of appealing against Mariam's sentence and for two juveniles convicted of affray over the incident.