A part-time waitress lent her spare mobile phone to a Facebook "friend" on learning that he did not have one, but ended up being hounded by him when he demanded to be reimbursed for the cost of repairing the phone.

Things came to a head when the two argued at a multistorey carpark in Toa Payoh Lorong 2, which ended with Ms Atika Dolkifli, 23, plunging 6.5m head-first to her death.

Her body was found only three days later on the landing of a lower floor.

Details of the events leading to Ms Atika's death emerged in the High Court yesterday when the man accused of killing her, Syed Maffi Hasan, 27, went on trial for murder.

He is alleged to have thrown Ms Atika over the parapet at Deck 5A of the Block 146A carpark between about 9.50pm and 10.30pm on Aug 31, 2015.

Syed Maffi, who is unemployed, initially denied having anything to do with her death, lying to the police that they had met but he did not see her again after she left to "meet her new boyfriend".

It was only when he was confronted with surveillance footage of him entering the carpark with the victim and leaving alone with her handbag, that he confessed he had attacked her in anger.

However, he may be challenging the admissibility of his confession during the trial.

Deputy Public Prosecutor Bhajanvir Singh told the court yesterday that Ms Atika's parents said she had a "lower than average intelligence level" but was able to work as a waitress at a Pizza Hut outlet.

Ms Atika first met Syed Maffi on Facebook in 2013. They reconnected in April 2015, after he was released from a drug rehabilitation centre. When the phone that she lent him had problems, Syed Maffi spent about $135 on repairs. But he lied about the cost and asked her for $300 as reimbursement.

He turned up at her workplace many times, and also went to her home but was turned away by her father.

Her older brother later told Syed Maffi to keep the phone and warned him not to contact Ms Atika again. However, on Aug 31, 2015, Syed Maffi called her and they met later.

Syed Maffi admitted that he pushed Ms Atika's chest, causing her to fall down a flight of stairs and hit the back of her head on the edge of a step. He then dragged her off the remaining steps to Deck 5A (of the carpark). However, it is a matter of contention whether he then threw her over the railing of the parapet or simply placed her there.

Surveillance cameras captured them walking into the carpark, but there was no footage of what transpired inside.

Syed Maffi claimed they had sex at the carpark. He said they later went to the roof, where Ms Atika demanded her phone back.

Syed Maffi admitted that he pushed Ms Atika's chest, causing her to fall down a flight of stairs and hit the back of her head on the edge of a step. He then dragged her off the remaining steps to Deck 5A.

However, it is a matter of contention whether he then threw her over the railing of the parapet or simply placed her there.

After she fell, Syed Maffi left her handbag inside a drain in Lorong 1 Toa Payoh, after taking her phone.

Ms Atika's father made a missing persons report on Sept 1.

If convicted of murder, Syed Maffi faces the death penalty or life imprisonment.