Integrity, ability and knowledge - these qualities are inscribed in the parchment presented by the Chief Justice to every appointed senior counsel.

In the four years since CJ Sundaresh Menon took office in 2012, only six lawyers have made the grade - as many were appointed in one year in 2008.

National University of Singapore law professor Ng-Loy Wee Loon is the latest addition, after she was appointed honorary senior counsel at the Opening of the Legal Year 2016 on Monday.

"A senior counsel is the highest level that a practitioner may aspire to attain. Every senior counsel serves as a role model for the rest of the profession, particularly on matters of ethics, responsibility and professional ability," said CJ Menon in 2014, when no applicant met the criteria.

He said then that key considerations would be outstanding advocacy skills over time and proven track records in public service or pro bono work.

The title is seen as a recognition of a lawyer's litigation abilities - and a strong selling point.

In the marathon City Harvest Church case that ended last year, all parties were fortified by senior counsel at some point.

For instance, senior counsel N. Sreenivasan defended deputy senior pastor Tan Ye Peng, while lead prosecutor Mavis Chionh was appointed senior counsel last year, when the trial was still going on.

It is arguable whether advocacy standards would have been different if the case had no such lawyers, but it does show that the senior counsel "brand" is a big draw.

"It's the senior counsel who are involved with the most important cases and who deal with the most significant legal issues of our day," said senior counsel Cavinder Bull when he was appointed in 2008.

Elsewhere, the title of senior counsel also serves as a benchmark for the best lawyer standards.

As Hong Kong's Chief Justice Geoffrey Ma said last year: "The title of senior counsel is not a status symbol... and the appointment of senior counsel is one that serves the public interest."