Yang Yin is an audacious and shameless man who believed that he was smarter than the law, said Judge of Appeal Tay Yong Kwang as he slapped a nine-year jail term on the former China tour guide for cheating a rich Singaporean widow of $1.1 million.

Yang, 42, was convicted in September last year of two offences of criminal breach of trust and sentenced to six years in jail. He had misappropriated the money from Madam Chung Khin Chun, now 90, in February 2010 and January 2012.

But yesterday, Justice Tay said that the original six-year jail term did not reflect adequately "the abhorrent nature of the accused's conduct leading to the offences and after they were uncovered".

Hearing an appeal by the Attorney-General's Chambers (AGC) for a longer jail term of 10 to 11 years yesterday at the High Court, Justice Tay said that general deterrence has to be the main sentencing principle.

"In every society, taking advantage of vulnerable persons in the community is completely unacceptable and utterly reprehensible. It must be denounced and deterred by sentences that reflect this sentiment in clear and strong terms."

He did not mince his words, noting that Yang had "claimed audaciously and shamelessly that he was a caring man looking after the needs of the victim as though she were his grandmother".

In reality, Justice Tay said, Yang had "eased his way smoothly, cunningly and methodically" into the victim's life over time to siphon off her assets.

He added: "Here was a man who obviously believed he was smarter than the law and, even when his game had been meticulously exposed by the very commendable work of the investigators, continued to play out his desire to beat the system."

It is obvious that the two crimes that he admitted to, Justice Tay said, were part of an "elaborate scheme encompassing practically all the earthly possessions of Madam Chung", including her sprawling bungalow.

"In all likelihood, the accused would have become a millionaire many times over if he had not been exposed by the victim's niece," he added.

Earlier, AGC chief prosecutor Tan Ken Hwee urged the High Court to set a new benchmark in sentencing and take firm and decisive action because Singapore's rapidly ageing society means more vulnerable seniors.

He cited two recent cases where elderly and vulnerable victims were cheated by people they trusted.

"The Singapore public has witnessed, through this case, elder financial abuse at its most egregious," said Mr Tan.

Yang's lawyer, Mr Irving Choh of Optimus Chambers, disagreed.

Mr Choh argued in a written submission that the six-year jail term was "not manifestly inadequate and should be upheld".

He said that Principal District Judge Bala Reddy, who sentenced Yang in September, had already considered the aggravating factors of the case and imposed a higher than normal jail sentence for the amount that was misappropriated.

Yang was also jailed for two years and two months in September last year for a slew of crimes over his immigration status, including falsifying receipts for a sham company in order to stay in Singapore and obtain permanent residency.

His PR status was revoked last year.

Appearing in a purple prisoners' jumpsuit yesterday, Yang, who has been in remand since October 2014, showed little expression at the one-hour hearing.

Mr Choh told reporters after the hearing that Yang had taken the news of the longer jail term calmly.

"(He felt) at least there was finality (to the case)," said Mr Choh.

Yang will now serve a total of 11 years and two months in jail.