SINGAPORE — The alleged murder weapon — a small knife that was never found — and where it came from look set to dominate the highly-anticipated trial involving the gruesome Kovan double killings.

On the opening day of the trial today (Oct 20), a defence lawyer grilled the widow of Mr Tan Boon Sin — who was killed along with his 42-year-old son, Chee Heong, on July 10, 2013 — on whether the knife could have belonged to the household, as they challenged the prosecution’s case that former police officer Iskandar Rahmat, 36, had gone to the Hillside Drive house intending to rob and kill Mr Tan in a “ruthless attack”. Mdm Ong Ah Tang, however, insisted that no knives were missing from her house, and she had never bought a knife with a serrated edge.

Mr Shashi Nathan, Mr Rajan Supramaniam and Ms N Sudha Nair are the lawyers defending Iskandar under a legal assistance scheme.

Mr Nathan told the court that Mr Tan had charged at his client with a knife. Speaking to reporters outside the hearing, Mr Nathan reiterated that the case was a “theft gone wrong”. Iskandar had planned to steal but things went awry and he killed Mr Tan and his son in self-defence, the lawyer said.

Iskandar told the police in a recorded statement that on the day of the murders, he had used the toilet in the elder Tan’s house. Upon stepping out, he wanted to grab a plastic bag containing over S$200,000 in cash and flee. But he claimed that before he could do so, Mr Tan, then 67, approached him with a knife. In the ensuing struggle, Iskandar used the knife to stab the elderly man multiple times across the face, neck, chest and hands. According to Iskandar’s version of events, the son entered the house and saw what happened. With his father lying bleeding on the floor, he charged towards the accused. Iskandar then attacked him, stabbing him in the scalp, face and right forearm.

After he fled the scene, Iskandar put the knife and his bloodied clothes in a bag and threw it into a canal at East Coast. The knife has not been recovered. “My client doesn’t deny stabbing them, but he never had the intention to kill,” said Mr Nathan, adding that Iskandar was unarmed when he went to the elderly man’s house.

The police had enlisted the help of a family friend to check if a knife was missing from a storage shed at the back of the house. The shed contained fishing gear belonging to the elderly man, who was an avid angler. The family friend, however, told police that no knives were missing from the stash.

Deputy Superintendent of Police Daniel Wong, who was the first of five witnesses called today, had also visited Iskandar’s house to search for the murder weapon. Three knives were seized from his house for investigation.

Taking the stand next for close to an hour, Mdm Ong was asked repeatedly by Mr Nathan if the murder weapon could have been taken from her kitchen. “I’ve never seen a knife with a (serrated edge). All the knives in my house have a (flat edge),” said Mdm Ong, 66.

About a week after the killings, the police had asked her go to the house and check if any knives were missing, she said. She had stayed away from the house following the deaths of her husband and son.

Mdm Ong told the police that no knives were missing. She and her late husband were the only occupants in the house. As she did all the household chores, she would know what knives she had at home, she said. Nevertheless, she was unable to recall how many knives the family owned.

Describing her late husband as someone whom “you can entrust your life with”, she testified that while he had a stubborn streak, he was not quick-tempered or unruly. “We would quarrel, but no matter how angry we got, he had never been violent,” she said.