In the months leading to his death in October 2016, a five-year-old boy was subjected to all kinds of alleged abuse, including being confined in a cage measuring 91cm long, 58cm wide and 70cm tall meant for the family's pet cat.

The 1.05m-tall boy was also allegedly pinched with pliers on his thighs and buttocks, hit with various objects and scalded with hot water. These acts of physical and psychological abuse were allegedly inflicted by his own parents, from July 2016 until his death on Oct 23 that year.

When the boy finally collapsed from his injuries that included severe burns across 70 per cent of his body, the married couple allegedly delayed sending him to the hospital for six hours.

Azlin Arujunah and Ridzuan Mega Abdul Rahman, both 27, allegedly did this out of fear that they would get into trouble for child abuse.

Deputy Public Prosecutors Tan Wen Hsien, Daphne Lim and Li Yihong said the couple blatantly disregarded the boy's welfare and his life.

"This is a murder as horrific as it is tragic," said the prosecution team in its opening statement yesterday in the High Court, on the first day of the trial.

"Leaving aside the physical abuse he suffered, one cannot imagine the pain and torment the deceased must have endured in the months leading up to his death. He was tortured to his death, and had no one to turn to," the team added.

His parents each face the charge of murder with common intention, which carries the death penalty, and charges relating to the ill-treatment of the child and voluntarily causing hurt by means of a heated substance.

The court heard that the boy was fostered out shortly after his birth and lived with a close friend of Azlin's in a private arrangement from around March 2011 until May 2015, when he was returned to the couple.

From June 2016, he suffered abuse allegedly at the hands of his parents while living with them and his siblings in a one-room flat in Toa Payoh.

In the week leading up to his death - between Oct 15 and 22 that year - the boy was scalded with hot water on at least four occasions, causing him to suffer severe scald injury that led to his eventual death.

The day before he died, the boy was hit on his head, hands and legs allegedly by Ridzuan, the father, using a broom, because he had refused to take off his shorts to have a shower.

Ridzuan then allegedly threw several cups of hot water at his son's legs and body, causing the child to shout "don't want, don't want" in Malay.

The prosecution team said the boy crouched over as Ridzuan poured hot water over his son's back and calf area, and the child fell forward onto the bathroom floor and stopped moving.

Upon his admission to KK Women's and Children's Hospital, he was found to be in a critical condition with symptoms such as low body temperature and low blood pressure.

He also had second-to third-degree burns, dehydration, acute kidney injury, multiple facial wounds and a broken nose, and demonstrated isolated speech delay.

Associate Professor Loh Tsee Foong, a senior consultant at the hospital's Children's Intensive Care Unit, testified in court yesterday that the boy also had severe anaemia that was "almost life threatening", suggesting significant blood loss over a period of time.

Prof Loh added that while he was told that the child had been playing with a kettle when it fell on him, he found the injuries to be "very suspicious". Despite the hospital's efforts to resuscitate him, the boy died about 14 hours later.

Ridzuan was arrested on Oct 23, while Azlin was arrested on Oct 25.

Psychiatric assessments of the couple during their remand found that they were both not of unsound mind at the time of the offences.

The trial continues.

Correction note: This article has been edited for clarity.