After rendering his lawyer's wife, Madam Low Foong Meng, unconscious using a padlock and a bicycle chain in their law office, Govindasamy Nallaiah, 70, allegedly looked for his case file.
But, unable to find it, he allegedly decided to set all the files on the secretary's table alight.
Then, a court heard yesterday, he waited for the fire to spread and for the office to be filled with smoke before he ran away.
This, knowing that the fire would block Madam Low's only escape path, and that the smoke and flames would kill her.
The prosecution yesterday gave its account of what happened on Aug 10, 2011, in the sixth-floor office in Afro Asia Building.
On trial for her murder under a charge which carries the death penalty or life imprisonment, Govindasamy disagreed on the witness stand that he had committed an act so imminently dangerous that it would, in all probability, cause Madam Low's death.
He maintained that he had hit her in a fit of rage. He said he had set his file on fire and fled after hearing the fire alarm, expecting sprinklers to be activated and security guards to save her.
But during his cross-examination by the prosecution on the seventh day of the trial, he was pointed to inconsistencies in his police statements and his court testimony. He had told police that he had hit Madam Low at least three times, but had said on Tuesday that he had hit her twice. Pressed to clarify, he said he could have hit her up to five times on the head.
Govindasamy had also told police that he had pleaded with Madam Low about his nine-year-old unpaid legal fee for about 10 minutes.
However, closed-circuit television footage showed that he was in his lawyer's office for only about seven minutes. "It appeared to me to be that long," he said yesterday.
Asked why he did not leave the law firm with his file, which he claimed he saw on a table, he said that he saw a lighter in the office, and the thought of burning it came to mind.
Govindasamy disagreed that he had taken along a disposable lighter to the office. Police had found three such lighters in his taxi, although he was not a smoker. But he said if he had wanted to, he would have taken all three.
He admitted, however, that he lied to the police that he forged his children's signatures on a promissory note to his lawyer, saying he did it to "save my children". They had signed on the note to stand as guarantors for his legal fee.
Madam Low's husband, Mr Rengarajoo Rengasamy Balasamy, had represented Govindasamy during a graft trial in 2002 for $25,000. The debt grew to $38,000 because of extra costs and interest.
On the day it was due, Madam Low's charred body was found in the office.
Asked if he had checked on Madam Low's condition before he fled the law firm that day, Govindasamy said that he did not. "I even forgot that she was there. That was the state of my mind," he said.
The trial continues next Wednesday, with forensic pathologist Johan Duflou giving evidence as a defence witness on Madam Low's injuries.