SINGAPORE - Just 2.5-hours after stabbing a father and son to death, Kovan double-murder suspect Iskandar Rahmat texted his superior officer in the police to apply for urgent leave.

Two days later, and an hour before being arrested at a popular Johor Baru eatery, senior staff sergeant Iskandar Rahmat again messaged his superior to say he had "run off" to Malaysia because of his financial problems and wanted to quit the force.

This was revealed on Tuesday (Oct 27) in Iskandar's trial, in which he has to answer charges that he murdered car workshop owner Tan Boon Sin, 67, and his 42-year-old son, Chee Heong, on July 10, 2013, during a bid to rob the former at his Hillside Drive terrace house.

Taking the stand on Tuesday was his superior, Senior Station Inspector Nurussufyan Ali, who heads an operations team of 35 at the Bedok Police Division. He told the High Court that he was "shocked" when he later learnt that his subordinate of six months had been arrested for murder.

"I did recall that there was an alert of a possible hit-and-run accident at Kovan, but I did not suspect at that point in time that it was a murder," he said .

Iskandar had fled the scene in the older man's silver Toyota Camry.

People driving along Upper Serangoon Road were shocked to see the body of the younger victim dragged under the car for a kilometre before it was dislodged outside the Kovan MRT station.

SSI Nurussufyan said the accused was posted to his team from the investigation branch in January 2013, when he came under scrutiny for chalking up debt more than three times his salary.

But Iskandar's performance was not affected by the investigations and disciplinary proceedings, he added. SSI Nurussufyan said he was a good worker, efficient and knowledgable.

Iskandar also seemed confident of clearing his debt, saying that he would get money from his cousin, he added.

The court has been told that no such cousin exists.

On the day of the killings, Iskandar was supposed to be on the night shift, but at 5.59pm, he asked for urgent leave to meet his cousin.

SSI Nurussufyan approved the request and told Iskandar to keep him updated.

At 10.17pm, Iskandar told him that he was "still talking". He fled to JB on his scooter at about 11pm.

At 8.49pm on July 12, Iskandar contacted his superior through WhatsApp and said he fled to Malaysia because he knew he would be made a bankrupt. Iskandar also wanted to resign from the force, despite attempts by SSI Nurussufyan to to talk him out of it.

Also taking the stand on Tuesday was forensic odontologist Tan Peng Hui, an expert on teeth marks.

Iskandar claims that the elder Mr Tan had attacked him with a knife and bit him during a struggle.

Dr Tan, who had examined Iskandar's left palm for bite marks the day after his arrest, categorically stated that the superficial injury on his hand was not a bite mark.

That prompted defence lawyer Shashi Nathan to suggest the possibility that the wound could have healed. But Dr Tan rejected this.

"Even with healing, you will see the formation of the scar, you will see physical evidence of teeth marks," Dr Tan said.

The trial, which continues on Wednesday (Oct 28), is expected to be over sooner than next year - when it was originally scheduled to run till.

This is because the defence is not disputing the testimonies of many of the prosecution witnesses, who no longer have to be called to the stand.

The court heard on Tuesday that the prosecution, which has so far called 15 witnesses, has just two more lined up.