Recoil from impact was the most likely reason the Sea Smooth public ferry and private motor launch Lamma IV separated two seconds after they collided, the inquiry into the Lamma sea tragedy heard yesterday.
But government forensic scientist Dr Cheng Yuk-ki said he could not rule out the possibility that the Sea Smooth deliberately reversed. He said the overall damage from the two led him to conclude that it was "more likely" the collision itself had caused the two vessels to separate.
And a smear of blue paint found on the front panel of Lamma IV's main deck indicated that the edge of the ferry's weather deck had reached that point.
"The collision between these two areas may have contributed some force, resulting in the disengagement of the two vessels," Cheng said, adding that broken fibreboard planking left inside Lamma IV's hull meant there was nothing physically joining the two vessels together.
Counsel for the commission, Paul Shieh Wing-tai SC, said: "It is not like a dagger being stuck into somebody's body and remaining there. It is a case where the tip of the dagger actually broke off and remained in the gash."
The Hongkong Electric-owned Lamma IV sank soon afterwards, killing 39 people who were on their way to watch the October 1 fireworks display.
Part of a report by commission-appointed naval architect Dr Anthony Armstrong, heard yesterday, said the two vessels were stuck together for two seconds. He found the angle of collision was 41.6 degrees, after considering the vessels' speed, instead of 30 degrees as stated in Cheng's report. Cheng also found that the two sidelights and masthead light of Lamma IV could have been on before the glass bulbs were cracked by sea water. He said only hot tungsten would react with air to form tungsten oxide and the presence of white powder on the filament he examined indicated the light was still hot when the glass bulb broke.
But Charles Sussex SC, for Hong Kong & Kowloon Ferry and the Sea Smooth crew, asked whether the white powder was sea salt. Commission chairman Mr Justice Michael Lunn ordered Cheng to carry out tests to confirm the chemical. The hearing continues on Monday.