SINGAPORE - A youth and his stepfather decided to take matters into their own hands after a 26-year-old man repeatedly visited their flat, and continued doing so even after the family lodged 56 police reports against him.

Ryan Xavier Tay Seet Choong, now 24, and his stepfather, Lawrence Lim Peck Beng, were so frustrated with Mr Shawn Ignatius Rodriguez that they assaulted him on eight occasions in 2015 and 2016.

Things took a tragic turn on July 9, 2016, when Tay assaulted Mr Rodriguez, who was then doing his national service with the Republic of Singapore Air Force, and the latter later died of traumatic asphyxia with a head injury.

On Monday (Aug 24) after a trial, District Judge Tan Jen Tse found Tay guilty of voluntarily causing grievous hurt to Mr Rodriguez.

Lim, now 58, was found guilty of abetting his stepson in committing the offence.

Before he died, Mr Rodriguez attended 10 counselling sessions at the Centre for Psychotherapy and Dr Nisha Rani found that he was possibly suffering from erotomania - an obsession and a belief that somebody loves the afflicted person.

Dr Nisha had earlier told the court that Mr Rodriguez was "obsessed" with finding out "the truth" from Tay.

But the court heard that Mr Rodriguez did not reveal what "the truth" was.

He was later referred to the Institute of Mental Health (IMH) and psychiatrist Susan Zachariah assessed him on July 7, 2016.

Dr Zachariah found that he could be suffering from Asperger's syndrome and obsessive-compulsive disorder.

But Tay assaulted him two days later. He died before receiving his definitive diagnosis.

Deputy Public Prosecutors Wong Kok Weng, Jason Chua and Chong Kee En had earlier stated in their submissions that Mr Rodriguez and Tay knew each other in 2006 when they were altar boys at the Church of Our Lady Star of the Sea in Yishun.

Tay, however, left eight years later as he felt that Mr Rodriguez was "fixated" with him.

Mr Rodriguez then tried to contact Tay by making frequent phone calls, and started loitering in the void deck of the latter's home at Block 279, Yishun Street 22.

The court heard that Tay and Lim assaulted him on eight occasions.

For instance, in June 2015, Tay used his right knee to strike Mr Rodriguez's face, causing the latter's mouth to bleed.

And in early 2016, Lim sprayed insecticide at Mr Rodriguez's face for one minute.

The prosecutors had said that in January that year, Tay's mother, Madam Irene Ng, filed a magistrate's complaint against Mr Rodriguez that led to mediation proceedings in the State Courts.

A mediation judge then told him stop visiting Tay. Despite this, Mr Rodriguez continued visiting the Yishun flat, the court heard.

On July 9, 2016, he visited the block on three separate occasions between 8.45am and 5.13pm. Madam Ng then called the police to report these visits.

At around 7pm, Tay told his mother that Mr Rodriguez was outside their home again. Madam Ng, who was out at the time, then texted her son, asking him to call the police.

The prosecutors said that instead, Tay replied he would "whack" Mr Rodriguez if he saw him.

They added: "At about 7.40pm, the deceased returned. Lawrence opened the door and shouted at the deceased for about five minutes and opened the gate intending to physically engage him.

"At this juncture, Ryan came out of the unit and the deceased started to run away. Ryan chased the deceased down the corridor and up the staircase at lift landing B."

A scuffle broke out between the two men and Tay later used his right knee to press against Mr Rodriguez's back even though the latter did not struggle.

Lim then sat on Mr Rodriguez's buttocks and performed a leg lock by crossing the latter's lower legs.

Tay rained punches on Mr Rodriguez's head before smashing it onto the ground, causing a "crack" sound and the older man's nose started to bleed.

Sometime later, some neighbours exited a nearby lift, and saw Tay and Lim on Mr Rodriguez.

The pair asked them to call the police and Lim also asked for a rope to tie up Mr Rodriguez.

The court heard that a few neighbours later brought items, including a rope and raffia strings.

One of them, Mr Lim Hock Piou, tied Mr Rodriguez's ankles, while Lim held on to Mr Rodriguez legs. Tay, meanwhile, continued to press his knee against Mr Rodriguez's back.

Police arrived at the scene before Mr Lim Hock Piou could complete tying Mr Rodriguez's legs.

Officers untied the unconscious man and a Singapore Civil Defence Force paramedic pronounced him dead at around 8.30pm.

Tay is represented by lawyers Peter Low, Andre Jumabhoy, Christine Low and Ashley Yeo.

During the trial, he admitted that he was angry and frustrated with Mr Rodriguez for stalking him.

He did not deny any of the acts of assault on Mr Rodriguez, said the prosecutors.

Lawyers Ang Sin Teck and Melvyn Low represent Lim, who had earlier testified that he could not remember what his stepson was doing.

The prosecutors told the court: "Lawrence claimed that he 'wasn't really observing' them. Lawrence then 'instinctively' sat on the deceased's buttocks and held onto his ankles."

The DPPs stated in their submissions that the direct cause of death was traumatic asphyxia due to the compression on the chest.

They also stated that Tay's "violent blows" caused multiple fractures, including to Mr Rodriguez's face, and these contributed to the traumatic asphyxia.

The prosecutors added: "The accused persons had taken the law into their own hands by participating in a vicious assault on the deceased, who was defenceless.

"They also claim that their motive was only to restrain the deceased and hand him over to the police. But that cannot be true given the violent assault on the deceased, which ultimately led to his death."

Tay and Lim will be sentenced on Oct 5.

For voluntarily causing grievous hurt, Tay can be jailed for up to 10 years and fined or caned. Lim cannot be caned as he is over 50 years old.