Of the hundreds of cases filed at the Supreme Court in the last decade, only a small fraction reached the highest court in Singapore as a criminal reference.

From 2007 to last year, a total of 21 criminal references were filed to the Court of Appeal, according to figures released to The Straits Times yesterday.

No criminal references were made in the last two years, even as the number of cases under the criminal jurisdiction filed at the Supreme Court stood at 526 last year and 509 in 2015.

The rare procedure was in the spotlight on Monday after the Attorney-General's Chambers filed a criminal reference, days after the High Court's ruling on the six City Harvest Church leaders. Their charges were reduced after two of the three judges ruled that they did not commit criminal breach of trust as an "agent", which the court connoted to be someone in a professional capacity.

Lawyer Lau Kah Hee, who specialises in commercial dispute resolution, stressed that a criminal reference is not a further appeal from a High Court's decision.

"It is not to be abused as a means of a 'backdoor appeal'," he said, adding that the High Court is the court of final appeal for criminal cases heard in the State Courts.

Rather, it is an avenue to settle a legal conflict, where there are questions of law of public interest arisen with a High Court decision.

He said: "Factual issues are not in play, since a criminal reference is not the same as a criminal appeal."

Other high-profile cases include one involving former National Parks Board assistant director Bernard Lim Yong Soon, who was fined $5,000 for lying to auditors.

His offence came to light after the purchase of 26 Brompton foldable bicycles in 2012 drew public scrutiny. The prosecution filed a criminal reference in 2014 asking the court to rule on whether jail terms should be imposed for public servants who lie during a probe.

The judges refused to make a ruling, as it was not appropriate to set a benchmark, as sentencing depends on the facts of each case.

In 2012, the prosecution filed a criminal reference, after former chief justice Chan Sek Keong set aside the conviction of Malaysian Adnan Kadir and ordered a retrial. Adnan had been sentenced to five years' jail and five strokes of the cane for importing 0.01g of heroin.

Mr Chan noted that if Adnan could convince the trial court that the drugs were for personal consumption as claimed he would be guilty of a less serious offence.

However, the apex court later ruled that the prosecution need not prove that an accused brought drugs into the country for the purpose of trafficking, in order to secure a conviction.

The judges, in a criminal reference, have the power to quash the conviction, make no orders to the acquittal or conviction, or order a retrial by the lower court.

The decision of the Court of Appeal in a criminal reference is final.