A maid who was having a nightmare that she was being hit woke to find one of her employers attacking her with a parang.

Alagerisamy Mohanadhas, who is unemployed, returned home from drinking six bottles of beer and slashed Myanmar national Phyu Sin Wai Aung while she was asleep on the sofa - wrongly believing that she had caused harm to his grandniece.

Yesterday the 60-year-old was sentenced to 4½ years' jail for causing grievous hurt to the maid at the flat in Lorong 7 Toa Payoh.

Deputy Public Prosecutor Teo Lu Jia said Alagerisamy got home in the early hours of Dec 26 last year and remembered how, he thought, the maid had treated his grandniece in a rough manner - although family members confirmed that Ms Phyu Sin Wai Aung was not responsible.

He found a parang with a 30cm-long blade in his room and slashed the victim on her face and right arm while shouting: "I see the devil in you." The maid did not retaliate as she thought she was having a nightmare in which someone was hitting her.

Alagerisamy's niece was woken up by the commotion and found her uncle holding the victim down and slashing her. She hit him with some photo frames but Alagerisamy stopped only when the weapon fell from his hands.

The maid woke up and realised that she had not been dreaming. When she saw blood on the sofa, she was terrified and started shaking in fear. Now 29, she had been working for the family for five years and has a good relationship with the rest of the family. She suffered multiple cuts on her right elbow, forearm and hands, and fractures on the elbow, forearm and finger. She was warded for four days, and still has decreased sensation in her right hand.

Alagerisamy was subsequently diagnosed with alcohol-use disorder.

DPP Teo, who urged the court to impose a sentence of five years, said Alagerisamy had used "excessive and gratuitous violence" in a situation where the domestic worker, a vulnerable victim, had done nothing to provoke him at all.

Pleading for a minimum sentence, Alagerisamy said that he regretted the offence, was sorry for what he had done, and added that he is suffering from diabetes.

District Judge Hamidah Ibrahim backdated his sentence to Jan 15.

The maximum penalty for causing grievous hurt by dangerous weapons or means is life imprisonment, or a term which may extend to 15 years. The offender is also liable to a fine or caning. As Alagerisamy is above 50, he cannot be caned.