A FORENSIC expert on Wednesday gave a detailed account, down to the hundredths of a second, of exactly how the fatal traffic accident that would cause Singapore's worst public order disturbance in more than four decades occurred.
Senior consultant forensic scientist Michael Tay showed how video footage was scrutinised and experiments conducted in a controlled environment to piece together how a private bus came to run over construction worker Sakthivel Kumaravelu.
Apart from taking precise measurements at the scene ranging from the lengths of road lane markings and distances between lamp posts, a 1.72m-tall model - the same height as Mr Sakthivel - was also used to re-enact the scene in field experiments.
"The landmarks are very important to us, because we can determine the speed of the bus at different segments of Tekka Lane," said Dr Tay, who was engaged by the Traffic Police to be an independent expert for the case.
Giving a blow-by-blow account of the accident on the first day of the Committee of Inquiry hearing, Dr Tay provided a frame-by-frame analysis of video footage taken from four cameras mounted on the bus.
Although it was shown in open court, the footage was not released to the media.
"The first time I saw it I was very troubled," said committee chairman G. Pannir Selvam.
"I don't want it to be released in public or on mass media. It would be irresponsible to show the video to the public."
One clip showed Mr Sakthivel, 33, being asked to get off the BT & Tan private bus after he dropped his bermuda shorts, first by an unidentified foreign worker, and then by timekeeper Wong Geck Woon.
After he alighted, the bus waited for a few more passengers before moving off along Tekka Lane at a speed of 4.2kmh. At that time, Mr Sakthivel was walking along the same road.
He chased after the bus as it passed him, walking beside the front passenger door and keeping pace at a speed of between 4.2kmh and 5.6kmh for 11 seconds.
But as the bus accelerated along the straight stretch of road to 9kmh, Mr Sakthivel gradually lost pace, disappearing from the field of vision of both the bus' mirrors and video camera for a good four seconds.
The bus then slowed down to 3.5kmh as it neared the stop line at the junction of Tekka Lane and Race Course Road. This was when Mr Sakthivel caught up, placing his right palm on the bus, although there was "no gripping point", said Dr Tay.
His hand was on the bus for 1.64 seconds before he tripped and fell into its path. The bus accelerated to 10.8kmh as it turned left onto the main road.
The forensic expert noted that the bus was "off-tracking" as it turned - a phenomenon where the rear wheels do not follow the same path as the front.
He estimated the off-tracking movement of the bus to be 1.51m, far wider than the assumed distance from Mr Sakthivel's palm to the midline of his body of 72cm.
"This had a pushing effect against the deceased. Then his right palm began to slide," said Dr Tay. As Mr Sakthivel fell forward, he landed face first with his head about 33cm in front of the bus.
"He did not move from his position, he had no time to react," noted Dr Tay.
As the bus turned, it ran over the fallen Mr Sakthivel - first over his torso, then his neck and his head.
The force exerted by the bus dragged Mr Sakthivel's entire body beneath its undercarriage, requiring the bus to be jacked up for him to be extricated.
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