Truck driver Shane Day, 47, is facing multiple charges, including dangerous driving occasioning death, after the tanker he was driving crashed and exploded in Mona Vale in October, 2013. A driver and a passenger from another vehicle were killed in the huge explosion and five others were injured.

Mr Day's committal hearing in the  Downing Centre Local Court court was told on Wednesday that, at the time of impact, Mr Day was travelling at 96k/h in a 70km/h zone.

The officer in charge of investigating the crash, Senior Constable Trent Wheeler, also said that there was evidence that the gear Mr Day was driving in was too high for the steep gradient of the hill he was travelling on when the crash occurred.

However, while Senior Constable Wheeler was under cross examination by Mr Day's solicitor, Dennis Moralis, it emerged that a re-enactment of the accident which forms crucial evidence in the case was entirely funded by Cootes Transport, the company which employed Mr Day.

Cootes was subsequently convicted of hundreds of road safety breaches and fined $500,000. The truck used in the re-enactment of Mr Day's crash was 8000 kilograms lighter than that involved in the accident, the court heard.

It also had fewer axles than the vehicle involved in the accident and did not feature worn brakes as Mr Day's truck did. "Wouldn't it be appropriate for the re-enactment to have been conducted by someone unconnected to [the incident]?" Mr Moralis said.

He further questioned whether such a test was "objective". Senior Constable Wheeler said he had been investigating the "driver not the company".

Later, the court heard that the brake drums on Mr Day's tanker were overdue for service and that the brake "shoes" were out of alignment. Only a mechanic could have determined that these defects were present, the court heard. The hearing continues.