The prosecution failed to prove its case in the trial of a former SMRT bus driver accused of a rash act while driving a public bus, leading to an acquittal yesterday.

Mr Zhang Kun, now 43, had been accused of driving bus service 700A above the speed limit of 50kmh before losing control of it while negotiating a sharp bend at the slip road of Bukit Timah Expressway towards Dairy Farm Road.

This happened at around 8.50am on July 21, 2013.

The bus fell onto its right side, killing Malaysian Sasikumar Gunasakaran, 18, and injuring Mr Ramanand Panday A Panday, 52.

After a 26-day trial, the Chinese national was acquitted of the two charges against him.

District Judge Michelle Yap noted that the prosecution could not determine exactly what Mr Zhang's speed was when he entered the slip road.

The prosecution had used speed data from the black box of the bus, and mapping the data out against its various locations, it submitted that Mr Zhang had entered the road at a speed of at least 56kmh.

But the judge said: "I do not think the prosecution had sufficiently proven that the accused's speed was at least 56kmh when he entered the slip road, and even assuming for the sake of argument that the accused was indeed travelling at 56kmh, it was not sufficiently proven that that this speed had caused the accused to lose control of the bus."

She also said the defence was not given an opportunity to conduct its own inspection of the bus.

The prosecution's expert inspected the bus between September and October 2013, and the vehicle was returned to SMRT by Oct 23.

Mr Zhang was charged in court about two months later.

The judge said: "According to the defence, some parts of the bus had since then been dismantled. It was not disputed that the bus was no longer in its original state immediately after the accident.

"What this meant is that the accused would not have been able to inspect the bus in its original state even if he had requested so immediately after he was charged. Undeniably, the accused had been disadvantaged in the conduct of his defence."

Mr Zhang declined comment.

His lawyer, Mr Anil Narain Balchandani, assigned by the Criminal Legal Aid Scheme, later told The Straits Times: "My client is drained from the process. He has been unemployed for (about) 37 months."

Those convicted of causing death by performing a rash act can be jailed up to five years and fined.

The maximum sentence for causing hurt by performing a rash act is a year's jail and a fine of $5,000.