A 50-year-old man who killed a 62-year-old woman he had known for a decade after she caught him stealing her jewellery was jailed for 18 years yesterday.

Rejecting the prosecution's arguments that former car washer P. Mageswaran should be given life imprisonment, the High Court said the case did not fall within the worst type of culpable homicide cases that deserved the maximum sentence.

Mageswaran was convicted in May of culpable homicide for strangling and suffocating Madam Kanne Lactmy in her Yishun Street 81 flat in 2013.

"This is a sufficiently stiff sentence to punish the accused for a heinous crime in which he has unnecessarily taken away a life, to deter the accused from committing further offences and to serve as a general signal that such acts are not to be condoned," said Judicial Commissioner Hoo Sheau Pheng.

She also rejected the prosecution's arguments that Mageswaran should get an additional six months' jail in lieu of caning. Those who are 50 and above cannot be caned.

Giving reasons for the 18-year jail term, she disagreed with prosecutors that the case fell under the worst type of culpable homicide cases. This was not a premeditated offence, she said, but a case of a robbery gone "terribly and tragically wrong".

She also noted that while the acts of strangulation and suffocation were undoubtedly vicious, there was no exceptional cruelty involved, which would place the case as being one of the worst types of culpable homicide. She also disagreed with prosecutors that there has been an abuse of trust and that greed was the motivating factor.

She accepted the results of neuropsychological tests submitted by the defence that Mageswaran suffered from mental impairments. These affected his control over his conduct when he killed Madam Lactmy on the spur of the moment to silence her.

She, however, agreed with prosecutors that due weight must be given to Mageswaran's long criminal record. She said he did not seem to have been deterred by the relatively stiff sentence of six years' jail and 24 strokes of the cane for a series of robberies in 2007.

Mageswaran used to work for Madam Lactmy's older son and was invited to their family gatherings.

On Dec 9, 2013, Mageswaran, who lived in Johor Baru with his Malaysian wife, arrived at Madam Lactmy's flat at about 8.35am and asked to borrow $2,000 to $3,000.

He needed RM5,000 (about S$1,600) for an instalment payment on his new flat. She said she did not have so much money.

When she went to brush her teeth, Mageswaran searched the flat and found a box containing jewellery and pawnshop tickets.

Madam Lactmy caught him and demanded that he return the box, but he pleaded for it. When she threatened to call her son, Mageswaran pressed a pillow over her face with his right hand, while he choked her with his left.

He left with the box and later pawned the jewellery for RM26,300. He used the cash to pay for his flat, and splurge on his wife and himself. He was arrested eight days later at Woodlands Checkpoint on his way back to Singapore.