Chua was arrested eight days later.
In mitigation, defence lawyer James Ow Yong said Chua has two young children, aged two and seven, with his second wife and the family is in Indonesia.
He had misplaced his trust in his friend and played a minimal role in the attack.
Justice Kan Ting Chiu noted that he was neither mastermind nor instigator in the attack.
When sentencing Chua to five years' jail, he said: "While not the instigator, the facts show that you have done nothing to stop the assault.
"There was no sign of remorse or compassion and we now know that even when you were called up by the police, you had initially denied knowledge or involvement."
Body dumped after brutal grab
1. Chia Kee Chen and Febri Irwansyah Djatmiko meet Chua Leong Aik at the substation. Chia has two knives, an electrode, a torch and a packet of gloves.
2. In the early hours of Dec 29, 2013, the men accost Mr Dexmon Chua at a multi-storey carpark. After hitting him, Chia and Febri bundle him into the van and electrocute him.
3. As Chua drives the van, Chia and Febri continue to beat Mr Dexmon. After a while, Chua stops the van and gets out. He takes a bus to the substation.
4. Chia drives the van to a live firing area in Lim Chu Kang, where they dump Mr Dexmon's body.
Horrific injuries
Mr Dexmon Chua's decomposed body was heavily infested with maggots when he was found. The injuries he suffered included:
- Extensive loss of scalp, especially around the front, top and right side of the head
- Loss of soft tissue on the face, including both eyeballs
- Fractures on his facial bones. His nose was broken and several teeth dislodged
- Fractures on his skull
- Internal bleeding in the brain
- Five broken ribs
Timeline of Events
Aug 2011: Madam Serene Goh, who is married to Chia Kee Chen, starts an affair with her colleague Dexmon Chua.
Nov 2012: Chia discovers romantic text messages from Mr Dexmon to Madam Goh. He confronts his wife, who admits to the affair. She ends the affair.
Feb 9, 2013: Mr Dexmon accidentally sends Madam Goh a Chinese New Year greeting over WhatsApp. Chia sees it and is furious.
April 2013: Mr Dexmon tells his sister he thinks he is being stalked by the driver of a Hyundai car.
Dec 24, 2013: Chia contacts his worker, Indonesian national Febri Irwansyah Djatmiko, saying he needs help killing a man who had raped his wife. He tells Febri to come to Singapore on Dec 26.
Dec 27, 2013: Chia and Febri meet at a substation near where Chia's old friend Chua Leong Aik is staying and they hatch a plan.
Dec 28, 2013: At about 10pm, the trio leave the substation and drive to a multi-storey carpark in Choa Chu Kang Avenue 4. At about 1am, Mr Dexmon appears. The trio attack him.
Dec 29, 2013: Febri goes to Malaysia with Chia, his wife and their two daughters. Febri goes to Indonesia by ferry the next day. Chia returns to Singapore on Dec 31 and is arrested.
Jan 1, 2014: Chia leads police to the live firing area off Lim Chu Kang Road. They find Mr Dexmon Chua's body.
Jan 8, 2014: Chua is arrested.