Odd job worker Wang Wenfeng was facing the death penalty for fatally stabbing a taxi driver nearly five years ago.
Instead, he was sentenced to life imprisonment and given the maximum 24 strokes of the cane in November last year.
In judgment grounds released yesterday, the High Court made clear in this rare case that it would impose the death penalty if prosecutors could show a life sentence would not be enough as a deterrent instead.
Justice Lee Seiu Kin, explaining why he decided not to hang Wang, said "the only evidence" prosecutors had produced in asking for the death penalty to deter others was this "single incident of murder in the past five years".
Wang, 35, had killed the taxi driver during a struggle in the course of a botched robbery.
He was originally handed the mandatory death sentence for murder but was re-sentenced following changes in the law effected last year that allowed judges to impose either the death penalty or life imprisonment for certain categories of murder.
Prosecutors had asked for the death penalty as a deterrent, arguing the offence was against a public transport worker and producing data on violence against cabbies in the past five years.
Justice Lee agreed there had been a number of cases of taxi drivers being seriously hurt. "But there is no upward trend nor are the numbers high - the range of such offences varies from two a year to seven a year in the last five years."
The judge said public transport workers spanned a wide range, from those who operated buses or trains with many passengers to taxis, which carried far fewer.
Said the judge: "The degree of punishment imposed could correspond to the degree of danger posed to the public."
He accepted that taxi drivers are especially vulnerable because they work alone and can be stranded in remote locations.
"However, it is one thing to impose a higher fine or period of imprisonment for an offence against a taxi driver to deter like-minded from carrying out offences against taxi drivers.
"It is quite another to say that it is necessary and appropriate to impose a sentence of death where life imprisonment is otherwise called for."
Justice Lee said deterrence was not a major factor in this case and the relevant "parameters" were the circumstances of the offence and that the victim belonged to a particularly vulnerable group.
The judge also took issue with prosecutors for suggesting there was a high degree of premeditation and planning on Wang's part - "without stating this was in relation to the offence of robbery and not the murder".
That "puzzling" submission "only had the unfortunate effect of causing the media reports of the case to be misreported", said Justice Lee.
Wang was armed with a knife and planning to rob when he got into the taxi driven by victim Yuen Swee Hong, 58, in the wee hours of April 11, 2009.
The Chinese national was desperate for money and asked to be driven to a lonely spot in Sembawang.
Once there, he demanded cash and a struggle ensued which led to the cabby's death.
Wang needed the money for an airline ticket and was nabbed two days later at People's Park Complex where he went to collect the ticket.
Prosecutors are appealing against the decision.