The jury in the trial of a Dublin Bus driver accused of dangerous driving causing death has been told technical evidence about the bus involved in the accident put forward by the prosecution was seriously inaccurate.

The jury was told today that technical data from the Dublin Bus vehicle was mixed up with information from a more powerful South African coach by an engineer from Volvo in Sweden.

51-year-old Kenneth Henvey from Palmerstown in Dublin has pleaded not guilty to dangerous driving causing the deaths of five people at Wellington Quay three years ago.

During the trial, the jury heard technical information about data downloaded from the engine of the bus driven by Kenneth Henvey.

The data was downloaded in December last year by Marcus Fasth, a specialist from Volvo in Sweden, the company who made the engine.

The results were given to gardaí and the prosecution team and made available to the defence shortly before the trial began.

Earlier this week, defence witness Dr Denis Woods, gave evidence about the possibility that Mr Henvey's bus had experienced a power surge.  

He said the Volvo data showed the bus had experienced engine speed surges for more than 26 minutes of its operating life and that it had generated excess power for almost half its operating time. 

Today, the court was told the Volvo specialist had been working on data from a much bigger, more powerful South African coach, at the same time as the Dublin bus.

Mr Fasth told the court he realised yesterday that figures from both buses had been mixed up in his computer program and he apologised to the court.

Judge Michael White said he had been assured by the prosecution and he accepted that this was a genuine error but he said it was a matter of serious concern.

Mr Fasth said analysis of the correct figures from the bus driven by Mr Henvey showed the engine had never behaved abnormally.     

He said if a fault was detected, the engine would shut down.  

Under cross-examination, he said he believed power surges existed but he said they are monitored and the engine would shut down. 

He said there was no evidence a power surge had occurred on the bus driven by Mr Henvey.

The court also heard there had been four complaints about power surges on a different Bus Éireann bus in Waterford but despite being examined three times no fault had been found with the vehicle.