Coroner Michael Chan Pik-kiu is expected to record his verdict today.

Li Zhenhua, mother of 20-year-old student Tong Qingtao, one of the four killed, made a submission yesterday, on the inquest's sixth day. A statement was read out by her daughter, Tong Ke, because Li was too distraught to do so herself.

'On the surface, the incident looks like an accident but I think the whole thing is all about the greed of the building owner and the principal tenant, the ignorance and arrogance of the contractor, and the inability and ruthlessness of the Buildings Department,' the statement said.

'The collapse was caused by the negligence of these people. My son was virtually murdered by them. People from the Buildings Department have no sense of responsibility and they are unprofessional. They said the building [posed] no immediate danger but they are now proven wrong. Either they are failed in their duties or they had misjudged ... they were the culprits.'

Li criticised landlady Chak Oi-luen and principal tenant Cha Nam-yam for their decision to subdivide flats in the building and for failing to hire a qualified repair man. She accused them of 'caring about money over lives'.

She told the court Chak's repair man, Chu Wai-wing, was a 'murderer'. Chu was using an electric saw to clear an illegal structure at the back of the block hours before the collapse, and government engineers believed his actions set off a chain of events leading to the collapse.

Lee Chui-sun, widow of Choy Toa-keung, 40, another casualty of the collapse, said her husband had been murdered or was the victim of manslaughter. She criticised the Buildings Department for not acting sooner over the state of the building.

The families of the two other victims were not in court.

Jolie Chao, counsel for the Buildings Department, said at worst it was a case of negligence, and called on the coroner to declare the collapse an accident. She earlier argued that the load-bearing column in the middle of the ground-floor shop nearest to where Chu had been working was the first to fall, triggering the collapse.

On Friday, two engineering experts who had helped the police investigate the accident contradicted Chao's argument, saying another column that had been severely weakened months before the collapse had broken first. The state of the column had earlier gone unnoticed by building inspectors, the experts said.

One of the experts, Eddie Lam Siu-shu told the court that the department had made incorrect drawings when analysing the state of the building, and said the block should have been evacuated months before the accident.

Chao replied that it was not necessary to rule on which column had collapsed first. 'Saying which column fell first would have implications on liabilities' in any future civil case, the lawyer said. 'There is yet other evidence we haven't considered.'

She said the issue of subdivided flats and their effect on safety was a social problem which would have to be tackled by a range of government departments, rather than the Buildings Department alone.

Shahmim Khattak, counsel for the landlady, also argued for a verdict of accidental death.