SINGAPORE - A Malaysian bus driver who was identified by a drug suspect as the person who handed her two packets of heroin escaped the gallows on Wednesday (May 19) after he was acquitted by the High Court.

Mangalagiri Dhruva Kumar, 50, was accused of driving into Singapore on May 16, 2014, and handing a bag containing the heroin to a woman named Shanti Krishnan.

In a written judgment, Justice Valerie Thean said the only evidence that Mangalagiri had supplied the drugs was Shanti's s testimony.

But the judge concluded that Shanti's evidence was not reliable.

Justice Thean noted that Shanti was not able to recall the various events of the transactions well. Shanti's testimony in court also deviated from her statements to narcotics officers, taken in the days following her arrest in May 2014.

Prosecutors produced phone records showing a total of six calls between Shanti and Mangalagiri on May 16, 2014, and on April 19, 2014. But the judge said that at most, this showed that the two knew each other.

Prosecutors also raised instances of suspicious behaviour by Mangalagiri, including a large volume of calls between him and an unknown number shortly after Shanti's arrest.

Prosecutors alleged that the number belonged to Mangalagiri's handler and argued that it was difficult to believe his claim that he did not know whose number it was.

But Justice Thean said the circumstantial evidence did not help to prove that it was Mangalagiri who had given the drugs to Shanti.

"In my judgement, the accused's guilt on the charge framed has not been proven beyond a reasonable doubt," said the judge.

On May 16, 2014, Central Narcotics Bureau officers arrested Shanti in Ang Mo Kio Street 61 and found $8,200 in cash on her. They also arrested Zainudin Mohamed, to whom she had passed the drugs.

The drugs recovered from the bottom of the rubbish chute at Zainudin's flat were found to contain 22.73g of heroin.

Shanti and Zainudin were convicted in September 2016; she is serving a life term, while Zainudin has been executed.

In a statement on May 24, 2014, Shanti identified the person from whom she had collected the drugs as the driver of a green and white bus.

On Sept 21, 2015, she was shown a collection of 17 photographs and identified Mangalagiri as the driver of the bus.

Mangalagiri was arrested at the Woodlands Checkpoint on Sept 23, 2015.

Immigration records show there were four dates in April and May 2014 when Shanti and Mangalagiri were concurrently in Singapore.

Shanti testified that apart from the May 16, 2014 meeting, she had met Mangalagiri for drug transactions on the other three occasions.

Mangalagiri contended that he did not know Shanti and had not passed heroin to her. Regarding the phone calls, he said he could not recall making them, nor what they were about.

The judge said this cast doubt on his credibility but did not prove the prosecution's case.

His assigned lawyers, Mr Ramesh Tiwary and Mr Satwant Singh, raised several arguments to show that Shanti's evidence was unreliable.

Justice Thean accepted that Shanti's statements regarding the first three transactions were inconsistent with her testimony.

The judge also accepted that, instead of testifying based on her recollection, Shanti had been "moulding" her testimony to match documentary evidence such as phone records.

"The prosecution submits that she has no reason to lie: In my judgement, in transactions such as the present where the stakes are high and the incentives opaque, such an assumption may not be made," said Justice Thean.