Two attackers slashed two victims in separate knife attacks on Sept 14, for no apparent reason.
Muhammad Taufiq Mohamad Raffi, 18, and Sivaraj Manickam, 19, had together targeted a man, 21, and a 16-year-old for contrasting "reasons".
They assaulted the younger victim, Muhammad Nasrun Isa, for smiling at them.
Mr Chen Cheng Jun was attacked because the pair thought that Mr Chen and his group of eight had been staring at them.
Both men were found guilty yesterday of voluntarily causing hurt and voluntarily causing grievous hurt.
The perceived staring incident had occurred after midnight when Mr Chen and his friends were smoking outside a McDonald's outlet in Hougang Avenue 8.
There had been no confrontation between the two parties, yet the duo decided to head to Sivaraj's home to get a kitchen knife and a sheathed baton knife.
With the knives tucked into their trousers, the two teens returned at about 2.30am. By then, most of Mr Chen's friends had left the outlet.
Taufiq and Sivaraj tailed Mr Chen and two friends as they left the fast-food restaurant. At Hougang Avenue 8, the pair sprang. Mr Chen suffered the most.
Sivaraj hit him on the head and face with the sheathed baton knife.
Taufiq slashed him on the left arm when he tried to block the knife swings. Fortunately, all three victims managed to escape.
Mr Chen suffered three lacerations, a fracture on his left forearm and muscle damage to the arm.
In the afternoon of the same day, Taufiq and Sivaraj hatched a plan to commit a robbery.
They bought watermelon knives from a shop in Serangoon Avenue 3.
At about 5pm, while prowling for a victim near Yio Chu Kang Road, the pair saw Nasrun walking towards them.
The 16-year-old made the mistake of smiling at the two. Both men were unhappy with his expression and the manner in which he walked, court papers revealed. They confronted Nasrun, but let him go.
Later, they decided to attack the teen as he was walking towards a bus stop. They kicked him on the back and slashed him on the head and body with watermelon knives.
The assault stopped only when a passing bus honked at them and the duo fled. Sivaraj kept his watermelon knife, while Taufiq got rid of this.
Nasrun was taken to hospital.
He had an 8cm slash wound on his left shoulder muscle, four lacerations to his lower back and injuries to his right ear and scalp. He was hospitalised for four days.
A doctor who examined Nasrun said his scarring will be permanent.
The two men will appear in court for sentencing on Jan 7.
UPSURGE IN YOUTH VIOLENCE?
District Judge Matthew Joseph displayed concern over the incidents, saying the two completely unprovoked attacks were "very serious".
Yesterday, the judge convicted Muhammad Taufiq Mohamad Raffi of voluntarily causing hurt and voluntarily causing grievous hurt.
A pre-sentencing report was ordered to see if Taufiq, 18, is suitable to be sent to the Reformative Training Centre.
Judge Joseph had agreed with Deputy Public Prosecutor Krystle Chiang's view that there would be "no room for probation in this (Taufiq's) case".
The judge said: "In the past three weeks, this court has heard three separate cases of youthful violence involving knives and serious slashing...
"Is there an upsurge (in violent cases) by youths?"
He was concerned the message has not gone out that the courts take a serious view against senseless acts of violence by youths.
Taufiq, a car washer, had played an equal role in the attacks from planning to execution.
He had taken the kitchen knife from accomplice Sivaraj Manickam's home.
While Sivaraj, 19, hit Mr Chen Cheng Jun with the sheathed baton knife, Taufiq likewise slashed Mr Chen repeatedly with the kitchen knife.
Later, the idea to rob somebody was suggested by Taufiq in a bid to obtain fast cash.
And it was Taufiq who had confronted Muhammad Nasrun Isa by asking the 16-year-old what his problem was.
This article was first published on Dec 18, 2015.
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In court yesterday, Taufiq asked the judge for leniency.