While intoxicated, a 40-year-old security guard attacked his son so savagely, it left the 15-year-old secondary school student with lacerations to his upper back and arm.

The wounds are likely to leave him with permanent scarring, Deputy Public Prosecutor (DPP) Joanne Leong told a court.

The boy had tried to snatch the 13cm-long blade from his father, who was wielding it while arguing with his wife in the kitchen of their home.

When the man's wife, 41, tried to stop him from hurting their son, he attacked her as well.

She sustained injuries to her hand, head and neck.

The man was yesterday sentenced to a total of 12 months' jail on a charge of voluntarily causing hurt to his wife, and a charge of voluntarily causing hurt to his son by dangerous weapon.

The man cannot be named as his son is a juvenile.

The court heard the security guard and his wife started arguing when the man arrived home at 11pm after a drinking session.

During the heated exchange, he became physically violent, hitting her with his hands before grabbing the knife.

The commotion woke their son up, who rushed out from his bedroom to see his father facing his mother in the kitchen, knife in his clenched fist.

Fearing for her safety, the youth ran forward to disarm his father. Enraged, the security guard swung the knife towards the teen, stabbing and slashing him on his arm and back.

The woman then tried to pull her husband away from the boy and attempted to snatch the knife away from him.

However, he struggled against her, pushing her backwards so that she fell onto the floor.

Eventually, the man stopped his assault, and the police were called.

They found him sitting on a sofa in his home, surrounded by bloodstains on the floor. He was arrested.

For voluntarily causing hurt, he could have been jailed for up to two years, fined up to $5,000, or both.

For voluntarily causing hurt by dangerous weapon, he could have faced up to seven years' jail, a fine, caning, or a combination of the three.