In 2017, the pattern reared its ugly head again in a tiny cell in Upper Hutt's Rimutaka Prison.
But why was it allowed to happen?
Corrections has remained close-lipped on how staff decided it was okay to put an 18-year-old prisoner in a cell with a violent sexual offender.
The Herald takes a look at the case at the conclusion of this week's trial in the High Court at Wellington.
How a vulnerable, teenage prisoner fell under the control of a violent sexual predator
When Goundar's victim arrived in the unit, he knew no-one, had no support, and was working to navigate his new reality.
The court has not revealed what he was in prison for, but the victim said during the trial this week he had been "in denial" about his own offending at the time.
Barely a man, he was the youngest person in the unit at just 18.
He said Goundar told him he was in jail for drug offending, and the older man persuaded him to request a transfer to his cell with the promises of movies, food, and a friendly face.
It only took until the first night for that friendly mask to drop.
The first two evenings, the victim said he was hit and slapped around the head and body for refusing to give Goundar sexual favours. By the third evening he was so beaten down, he was forced to give in to Goundar's demands for oral sex.
From there, the degrading activities continued nearly every night for two and a half months, with regular beatings from Goundar to keep his victim submissive.
The abuse escalated, with Goundar raping the victim multiple times and at times threatening to kill him if he told anyone or tried to move to a different cell. On one occasion he produced a shank, which looked to be made from a piece of plastic cutlery.
The victim, terrified for his life, held his tongue. Despite the pain he was suffering from the rapes, he avoided seeking medical treatment for fear someone would put two and two together, and Goundar would seek revenge for being exposed.
He was convinced Goundar would find a way to hurt or kill him if the truth came out. Even if the older man was moved to another prison, he could send a letter through the prison mail system to his friends in the unit and they could harm the victim on Goundar's behalf, he believed.
There was a window to the cell for guards to look through on their rounds, but Goundar kept it covered with a blanket or sheet of some type.
The abuse only stopped when a mystery caller contacted Crimestoppers, an anonymous tip-off service, threatening violence against Goundar for his attacks on the victim. Everyone involved in the trial including the victim said they did not know who placed the call.
Goundar was moved out of the unit, but even then the victim was too scared to speak to police when approached.
It wasn't until six months later, when news of the abuse had spread through the unit and the victims fellow inmates had assured him they would not let him be harmed, that he wrote a letter to police about what he had endured.
In his evidential video interview with police, the victim told officers he was still afraid of retribution for speaking to them.
Why was an 18-year-old placed in a cell with an aggressive child sex offender?
It's unclear how thoroughly Corrections assessed the compatibility of the two prisoners before allowing the younger man's move to the cell.
Corrections uses a system called the Shared Accommodation Cell Risk Assessment, or Sacra, to reduce the level of risk prisoners pose to each other when placed in shared accommodation cells.
Staff should assess the usual things such as gang affiliations, health needs and risk of violence towards others.
The list also factors in the prisoners' previous behaviour and history, the nature of their offending, and their risk of sexual assault against others.
At the 2013 sentencing for his earlier offending, Goundar was assessed as being at a high risk of reoffending.
Corrections chief custodial officer Neal Beales today told the Herald a sexual conviction did not necessarily preclude a prisoner from being double bunked.
"While a prisoner's previous convictions are considered during the assessment process, there are a multitude of other factors that are relevant," he said in a statement.
"However, staff are directed to consider sexual predation when considering suitability for a shared cell and no prisoner who poses a detectable threat to another prisoner will be double-bunked."
Beales would not comment on how Goundar's case was assessed, citing legislative obligations under the Privacy Act 1993 and the Official Information Act 1982. He also would not say whether Corrections would be providing compensation to the victim.
He expressed his "deepest apologies" to the victim.
"No one, no matter who they are, deserves to have endured what he had to endure at the hands of Mr Goundar, whether they be in prison or not. We know the outcome of the court case this week will do little to erase what has happened, but we do hope it is at least a step towards helping him move on."
A spokesman for Corrections Minister Kelvin Davis said it was the minister's "strong expectation" that Corrections "does everything possible to keep people safe while they're in prison".
He declined to comment further while the matter was still before the courts.
Red flags
In assessing Goundar's suitability for double bunking, Corrections could have looked at the facts of his 2011 offending.
The incident bears concerning similarities to what he would go on to do to his cellmate.
In both cases, Goundar targeted a young, vulnerable victim by initially presenting a friendly face.
He then isolated his victims - in the first case by driving them to a secluded area, and in the second case by getting him alone in a cell after lockup.
Goundar then demanded oral sex, and when he did not get his way he resorted to hitting his victims around the head until they complied. Both cases escalated to rape, and involved threats to kill the victims if they did not submit to him.
Where to from here for Benjamin Goundar?
Goundar, who is still in prison for the original offending, will be sentenced for the latest offending in February next year.
The jury of eight men and four women yesterday found him guilty on nine charges, including common assault, sexual violation, and threatening to kill.
He was already serving a 16-year prison sentence for the 2011 offending, but may now be a candidate for preventive detention.
This sentence is similar to life in prison, in that it is an indefinite sentence while allows an offender to be kept in jail for as long as they are considered a risk to society. They can also be recalled to prison at any time.
O'Sullivan yesterday asked Justice Karen Clark to order a report into whether Goundar would be eligible for such a sentence.
Where to get help:
• If it's an emergency and you feel that you or someone else is at risk, call 111.
• If you've ever experienced sexual assault or abuse and need to talk to someone call the confidential crisis helpline Safe to Talk on: 0800 044 334 or text 4334. (available 24/7)
• Male Survivors Aotearoa offers a range of confidential support at centres across New Zealand - find your closest one here.
• Mosaic - Tiaki Tangata: 0800 94 22 94 (available 11am - 8pm)
• If you have been abused, remember it's not your fault.
• Wellington HELP has a 24/7 helpline for people who need to speak to someone immediately. You can call 04 801 6655 and push 0 at the menu.
