A group of motorcyclists tailed Mr Jerome Loy Xue Song and assaulted the motorist, leaving him with a bloody head.
A district court on Tuesday sentenced Shadikin Noordin, 25, one of the motorcyclists, to four months in jail after he pleaded guilty to punching Mr Loy.
Just after midnight on June 16 last year, Mr Loy, 24, then a student, was driving his car along Geylang Road when he noticed some motorcyclists riding in a zigzag manner. He slammed his brakes when two of them suddenly rode in front of his car.
This made them unhappy and they tailed him to Hill Street. There they surrounded the car and rode very slowly.
When Mr Loy had to brake suddenly again, Mr Sharulizad Sukiman, 26, was unable to stop in time and his motorcycle hit the car's rear and fell to the ground.
His pillion rider, Siti Khadijah Hussain, 24, was enraged and hit Mr Loy's cheek with her slipper. She also punched him. When he grabbed her wrist, some of her companions set upon Mr Loy.
A witness called the police. The attackers did not ride off as Mr Loy had seized one of the motorcycles' ignition keys.
At the Singapore General Hospital, Mr Loy received three stitches for the cut on his scalp.
Shadikin's defence counsel, Mr Paul, who goes by one name, said that Mr Loy had provoked his client by revving his engine unnecessarily. Shadikin, who is a hotel executive, could have been jailed for up to two years and fined.
The other accomplices have already been dealt with. Siti Khadijah and Muhammad Zulfadly Zainoldin, 22, are serving 15 months' probation. Mohammad Yassin Abdul Latif and Muhammad Firdouz Saiman, both 24, were jailed for four months each.
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