Yap would help the brothers to prepare their daily necessities and gave them whatever they wanted, and he would not resort to physical force when he disciplined the twins.
In December 2021, Yap began to harbour suicidal thoughts, and even bought an ice pick with plans to take his own life.
At the start of 2022, the boys were about to be assessed for their suitability to remain in their mainstream primary school, and this turn of events caused Yap's wife to become more depressed and infuriated at her sons.
[6][7] On 21 January 2022, Xavier Yap decided to carry out his murder plot at a playground near his house in Greenridge Crescent in Upper Bukit Timah, where he often brought his sons to play.
[8][9] After the boys were dead, Yap attempted to kill himself several times, using the ice pick, a tree branch and a rock.
None of his attempts were successful, and as a result of these failures, Yap decided to put up an act that he was the victim of an attack, and would lie to the police about it.
Yap believed that this lie would be disputed by the evidence and it would give the impression that he had no remorse, and he could be given the death penalty for murder as a wish to join his sons in the afterlife.
[27][28][29] In November 2022, Yap, who was still in remand awaiting trial for the double murder, discharged his previous lawyer, Anil Singh Sandhu, and engaged a new four-member defence counsel, consisting of veteran criminal lawyer Choo Si Sen and his daughter Choo Yean Lin, their law firm associate Patrick Nai, and Muhammad Razeen Sayed Majunoon from another law firm.
DPP Kumarsen argued that the victims in this case were vulnerable children diagnosed with autism, and Yap had taken meticulous steps to lure the boys and killed one of the brothers, Ethan, in front of the other twin, Aston, and ensured that both of them died by pinning their heads in the canal water.
Choo also stated that Yap, who had since filed for divorce, chose to kill the twins at the playground in Greenridge Crescent, thinking it was "a good place to end all their lives together," as he had taken the boys there to play a few times.
Yap also wrote that he changed his mind after discovering from his friends and family that his wife was allegedly not saddened and nonchalant at the death of the twins and threw out their belongings, and even invited her lover to stay in their matrimonial flat, and he thus decided to fess up with everything and expressed his wish to take care of his mother upon his release, and study for a diploma or degree in order to do social work at welfare organizations to help children with similar conditions as his sons.
In his judgement, Justice Hoong stated that Yap had committed a set of "heinous and serious," yet tragic, series of atrocities that gripped the whole of Singapore back in January 2022, and he stated that rather than caring for the boys, Yap had inflcited upon them "serious and irreparable harm" by killing them, and had betrayed the trust placed upon him as a parent when he killed his twin sons, who were vulnerable children diagnosed with autism and global developmental delay.
Justice Hoong stated that while the penalty he was about to impose was in no way a compensation "for the tragic loss of two innocent young lives", the purpose of the sentence was to make Yap reflect on the irreparable harm he caused to his surviving family members by acting under the misconception that he was "easing the suffering and pain of the victims and of those around him".
[43][6] Justice Hoong also stated that just because Yap was diagnosed with depression and suffered from diminished responsibility, it was not by any means an excuse for his wickedness, and rehabilitation should not become the key consideration for sentencing.
Justice Hoong pointed out that Yap was able to differentiate right from wrong and his conduct was founded on fact and not delusion, based on the assertion of his wife's alleged affair and abuse of their children, and he could also understand the nature and consequences of his actions and plan the killings beforehand.
Having noted the severity of the double killings and the nature of these crimes, Justice Hoong concluded that it was necessary to mete out an appropriate punishment to match the magnitude of Yap's actions, and it would also be morally unjust to commit Yap to serve concurrent sentences for killing his sons, since both Ethan and Aston had an equal right to life despite their deaths occurring as a single transaction.
[44][45] As such, Justice Hoong sentenced 50-year-old Xavier Yap Jung Houn to seven years' imprisonment for each of the double manslaughter charges.
Member of Parliament Sim Ann for Holland-Bukit Timah GRC, as well as religious leaders like Imam Mohd Idris from Al-Huda Mosque, Venerable Rui Zhen from Beeh Low See Temple and Father Francis Lim from the Church of St Ignatius, had attended an inter-faith prayer session conducted at the canal.
Legal experts analyzed that one's potential to commit murder may arise from several compounding factors, which include mental conditions, stress and personal circumstances, and it was more plausible for a murder to happen within the family given that there was a higher rate of opportunity to strike on the account of close familial ties and shared living arrangements, not discounting any other relevant compounding factors.