He didn't tell her he picked out somewhere to dump a body before running his car off the road into Mrs Gotingco. She was struck so hard one leg broke in two places before she was flung across the bonnet to smash the windscreen.
He didn't tell her he bundled the mother-of-three into the back of his car and drove her to his home where he raped then murdered her.
He didn't tell her about cutting Mrs Gotingco's throat, spilling blood on the floor of his garage - in an apartment his mother paid for with wages earned scrubbing toilets because she wanted her son to have the best shot she could give him.
Instead, when Robertson, 28, told Mrs McWatters, 45, how Mrs Gotingco died it was sugar-coated to cloud the awfulness as much as he could.
But then, he's never told her everything.
Suicide attempt after child abduction arrest
The one time Mrs McWatters actually considered her son was guilty of something truly awful, when he was arrested for child abduction in 2005, she says she tried to kill herself.
"When the police come and saw me and they told me he did it, I tried to kill myself."
In an interview with the Herald last year, in the months following Robertson's arrest, she said she wondered: Is it me? Is it how I raised him? Is it genetic?
"I went through all those things," she says.
"I was upset that I thought my son had done it. I couldn't believe it. I didn't believe it.
"But they put things in my head and they made me believe that my son had done it until I went to see my son in jail and I spoke to him and I could tell in his voice and see on his face that he didn't do it. That's when I started supporting him and stuck by him 100 per cent."
She found the strength to go on because he told her he was innocent. He won his mother's support and never waivered, declaring - as she does - his innocence to anyone who will listen.
'It was a stupid accident and he panicked'
This time, he told her it was an accident.
"It was a stupid accident and he panicked. I feel so, so sorry for the family. So does my son. He just can't stop crying. He's so upset about the whole thing. He keeps saying he wishes he could take it back, he wishes he could go back to that night and change everything.
"He knows [that he faces a long stretch in prison]. He knows he's done wrong and he's prepared to accept his punishment. To him it's not enough for what's happened. No amount of punishment could make him feel any better for what he's done."
Oh yes he was angry that night, May 24 2014, when Mrs Gotingco was killed, she says.
He had been released from eight long years in prison, which felt longer because he refused to concede the charges on which he was convicted.
"He was angry but he wasn't angry enough to kill anybody."
He'd been to see his father, who had nothing to do with his upbringing, earlier in the day.
He had no job, no training schemes lined up, no prospects.
The week before his aunt Cherie Fyfe had died. She had, along with his mother, been a staunch supporter of his innocence.
He wasn't allowed to travel so couldn't get to her funeral, or see his mother who had suffered a mild stroke.
"He couldn't get to me and I couldn't come to him," she says.
"He was drunk and he was driving his car and he run this lady over by accident. And then panicked. He didn't know what was going on. He said it was like he stepped outside his body and wasn't in it.
"He was emotionally upset. It was hard to talk to him. He kept saying how sorry he was, that he had taken a life and he was so upset.
"That's not my son. He would never hurt a lady. He had to be devastated over his aunty's death to have done something like that. It started out as an accident and he just panicked.
"I just can't get my head around it. It's not something I would ever think my son would do because he's such a gentle person towards me."
'His life is going to be in jail now'
For all the excuses Robertson made, Mrs McWatters' estimation that her son's going back to prison for about 25 years suggests she knows it was more than an accident.
"I'm not going to get to have a relationship with my son," she says. "His life is going to be in jail now. I'm not ever going to be a grandmother.
"It's pretty hard to deal with the fact that I've lost my son but I suppose it's not as bad as the family. I feel so sorry for the family - they have lost a mother, a grandmother, a wife. My heart goes out to them."
Mrs McWatters tries to find a little good in anything her son did that night. Mention the cemetery, where Mrs Gotingco's body was dumped, and she says: "At least she wasn't dumped on the side of the road, or chucked in the river. He tried to do something right."
It might have been better had she not tried to find the good.
Tony Robertson's early life
Maria McWatters falls to tears when speaking of Robertson.
She remembers how young she was when he arrived, just 17. She remembers how little he was. Babies having babies, she laughs, and not just a little sadly.
He arrived in Ngaruawahia, on the banks of the Waikato River, but she turned her back on the town almost immediately after.
Robertson's biological father, her much older lover, stayed behind. She says "we just grew apart", something she's not at all sorry about.
Mother and baby, Maria and Tony, went back to live with family further up the Waikato River in Mangakino.
There they stayed for six or seven years, until she realised the lack of jobs and any other prospects were robbing her of that which was most important: "To give my son the best things in life. I love to work and I love to give my son things he deserves. You can't do that on the dole."
They moved to Tauranga, which was home until his arrest on the charges which would send him to prison.
"My son is a good boy," she says. "He is always very polite. He never swore at adults. He's so respectful to women which is why this whole thing is such a big shock."
I raised him that way, she says, proud. "Respect your elders. He always respects me."
But as Robertson grew into adolescence, court records show the rest of society saw less of the "good boy" than his mum did.
Mrs McWatters recalls, then, how he had joined with "a couple of the wrong people and got into drugs", meaning cannabis. Police Youth Aid helped hugely with his misdemeanours, which were "nothing nasty", she says.
His record suggests otherwise. It starts in 2003, when he was aged 16. In two years, he was convicted on four common assaults, assault with intent to injure, along with threatening and disorderly behaviour among other minor crimes.
Robertson's record turns nasty
In December 2005, it definitely turned nasty. Robertson, a jury later found, mugged an 11-year-old for his cellphone which had a new and modern camera facility.
Not long after, he sought out children and tried to lure them into the Mistubishi Lancer he was driving. It was December 14; he told a 6-year-old and 7-year-old their mother had Christmas presents for them and he was to take them to her.
They pondered the offer as another child raised the alarm. As an adult emerged he drove away. The number plates on the car - front and back - had been removed.
The next morning, Robertson was again hunting children. A 5-year-old-girl walking to school with her brother aged 7 was lured with the promise of mother and presents.
Robertson pretended to talk to the girl's mother on the cellphone taken in the mugging, convincing her to get in the car.
Then away he went.
There were heroes that day - the girl's big brother ran to school and told a teacher, who told a deputy principal who rang police. There was the police officer, Sergeant David Thompson, who checked out the remote Kaiate Falls Rd on a hunch and found Robertson at the side of a rural road, the sobbing girl inside his car.
Robertson denied abducting the girl, saying he had seen her, lost and sad, and stopped to help. She described an indecent assault and Robertson's desire to photograph her bottom and boxer shorts (the cellphone picture memory was empty when found).
Robertson, who had an answer for everything in court, couldn't explain how the girl's pink-and-cream Barbie boxers, with pink bows and hearts, were in the footwell of the back seat. The girl, sobbing, took refuge in Sergeant Thompson's car.
She told him: "The man hurt my heart."
In the High Court at Tauranga, Robertson took on Crown prosecutor Simon Bridges - now a Minister of the Crown. He wasn't shy, cussing and raging from the witness dock as he accused police of tampering evidence, witnesses of getting it wrong, and others of lying.
He showed himself to be well-versed on the evidence. In one exchange, he told Bridges: "I have every statement in my cell and read through it word by word and you can clearly see (witnesses) have been manipulated."
DNA testing for saliva showed nothing.
Robertson went for Bridges: "Did you find any of my DNA on her? Did you find any photos on that (cellphone)? You didn't. You have got nothing. All you have got is your f***ing word. You have no DNA. She is saying this c*** licked her (leg). Surely if I licked her leg you would have found my DNA on her?"
At one point, Bridges challenged him on an answer he had given and Robertson spat back: "Brush your hair back behind your ears so you can hear me."
Robertson got eight years. Bridges unsuccessfully sought preventive detention after psychological reports assessed Robertson as having a "high risk of further sexual offending following release from prison" without psychological treatment.
Salvation in Robertson's proclaimed innocence
By then, Mrs McWatters had found salvation in Robertson's proclaimed innocence. She says the absence of her son's DNA shows he was stitched up. The Court of Appeal and Supreme Court disagreed.
Her fervour wasn't shared by others. "It was horrible the way I was treated. I couldn't deal with it. I left town, left all my so-called friends and went to start a new life and stuck by my son 100 percent. I knew he didn't do it."
She moved to Hamilton in 2006 and then, in 2008, met her future husband and together they moved to Australia. She went from earning $16 an hour as a nurse aide's to scrubbing toilets for $28 an hour.
Again, it was for Robertson. "I came back here to earn money so when my son got out I had money to help set him up."
Robertson refused rehabilitation programmes
Robertson did little with his time in prison but let it pass. Mrs McWatters visited from Australia once a year and they spoke by telephone on weekends.
By 2010, a Parole Board report showed Robertson had acknowledged violent offending but rejected any suggestion the abduction had a sexual element. He refused rehabilitation programmes - fulfilling the sentencing judge's prediction years before that he would be unlikely to seek assistance.
The report includes a note from a prison officer saying "his (previous) behaviour was appalling and he was getting into all sorts of trouble with the prison". He was "an unmotivated young man with both bad behaviour and non-compliant attitudes".
Robertson appeared to conform to prison standards through the year, but when parole was declined in March 2011 he went off the deep end. The next report records two misconduct findings, including one which involved a weapon found hidden in his cell.
A 2013 report stated he had not taken part in any programmes in prison and had specifically refused to take part in the Kia Marama sex offender treatment programme.
As the end of 2013 approached, there was nothing the system could do to keep him inside.
Reintegration to society
He had been assessed as high risk, prompting the Department of Corrections to seek an Extended Supervision Order (ESO) - a court order to monitor prisoners considered at the greatest risk to society for a period of up to 10 years.
Until it was obtained, Robertson would be monitored under Parole Board release conditions. He was told he would be subject to GPS monitoring, which he was unhappy about, but agreed to along with conditions barring contact with children.
He told the Parole Board his mother was arriving a month before his December release to find him a home.
Mrs McWatters was not the only one waiting for his release. Robertson's girlfriend from 2005, Glenys, was also there. Mrs McWatters said she saw someone else after Robertson was arrested in Tauranga, having a child with them, but then decided to wait for him.
"She loved him." They were together after his release and were still together after his arrest for murder. "She has said she'll wait but she isn't going to wait 25 years. Can't expect the poor girl to put her life on hold."
The preferred option release was Matamata, with an uncle on a farm. It was rejected. Then there was the apartment in Birkdale, over which there was also a scrap.
It was a huge disappointment. The apartment had been furnished - everything made ready for Robertson to have as fine a reintegration to society as a prisoner ever had.
Robertson, instead, was assigned a pokey flat in central Auckland. "This is when he first got out and he was stuck on his own. He had no support in this flat."
'It was like they were baiting him'
Then came the breaches. The first was when a cousin came to stay - a breach of the flat rules. Mrs McWatters says there was a technical breach - Robertson and his girlfriend near a dairy, not realising he was on the edge of the park. He was back in court and angry.
"I didn't even know that park was there Your Honour," he told Judge Roy Wade.
"Because you fellahs just judging on the f***ing s*** that I was charged with in the f***ing past man. I haven't f***ing committed any crime."
Mrs McWatters saw her son as a pawn in a rigged game. "It was like they were baiting him and pushing him so he would end up back in jail."
Family was trying hard and she had plans to come back to New Zealand. "We were there for him and we wanted to make sure that he got the best and got ahead in life again and not just sat stagnant so he would end up in trouble. We were trying to do the right thing by our son, get a job and set himself up and just be somebody.
"They just wanted him to sit at home and be nobody."
It is clear, from the evidence put forward at the hearing for the ESO, others saw a different man - a dangerous man.
Kirsten Tolond, a psychologist who assessed Robertson, gave an opinion which was prescient.
She told Justice Edwin Wylie that Robertson had troubling social influences, hostility to women, a sense of social rejection, a lack of concern for others, poor problem solving skills, impulsive behaviour, deviant sexual preferences and a sexual preoccuptation. He showed "no empathy", a "sense of entitlement" and a habit of blaming others for his behaviour.
Ms Tolond told the court there was a "high risk" Robertson would re-offend on release against victims likely to be girls in public places who he didn't know, placing them at risk of abduction and sexual violence.
There was also, she warned, a tendency for Robertson to "impression manage" - conning people into thinking he was different from what he was.
Judge Wylie gave the order for an ESO, which was ultimately pointless. Robertson killed Mrs Gotingco before the order came into effect.
But it was clear. Robertson was officially a danger to the society into which he was allowed to live.
Some close to the case believe Ms Tolond was exactly accurate, right down to Robertson's intended victim. It was dark by the time Mrs Gotingco got off her bus, having worked overtime on a Saturday. It was raining. The woman, described as "small, petite", could have been mistaken for a child in the early evening.
Robertson was stuck on the same road he travelled in 2005. In his car, hunting children.
A predator who, once successful, used the car to carry his victim away. There was a cop with a hunch who saved the girl in 2005. No one could save Mrs Gotingco.
Her son called police at 3.30am. An hour later, with his sister, they tracked their mother's iPhone and found it just a few hundred metres from home and safety. It was there, on the ground with her lunchbox, where Robertson had run her down.
Mrs McWatters flew back to Western Australia from her sister's funeral in Melbourne. Her husband collected her from the airport and broke the news - Robertson had been arrested, a woman had been killed.
She spoke to him. "He said he just felt worthless. He couldn't be there for me when I got sick, he couldn't be there for his aunty, he couldn't get a job and it just all got to him so he just got drunk."
He told her he was planning on calling the detective in charge of the case. "He was going to talk to him about everything. He didn't want his lawyer to enter no plea. He wanted the family to know how sorry he is. He is ready to take his punishment.
"As far as plans go, he hasn't got any. He's going to jail and he knows it."
Robertson never made the call - or if he did, it was under the terms on which his defence was based - that it was an accident.
Did he "impression manage" his mother? Instead of confessing, he used every opportunity since then to attempt to have evidence ruled out or to have the case put off.
He squirmed and wriggled away from the facts of the case, as if every bit of evidence placed responsibility on his shoulders, took from him the stories he would tell his mother.
Detectives found Mrs Gotingco's blood in Robertson's car, in his apartment and on the knife he used to kill her. They took samples of Robertson's semen from his victim's body, and traced the sheet in which he wrapped and dumped the body.
Astonishingly, Robertson committed the crimes wearing a GPS anklet. Detectives traced him from the cemetery before the murder, to the street both when and where Mrs Gotingco went missing and then back to his apartment before his 8pm curfew.
They followed the path on the map, learning that Robertson had left the apartment just after his curfew ended at 6am. The path led to the cemetery, where Mrs Gotingco's body was found.
They backtracked to his home, the murder scene, arrested Robertson and charged him with murder which was forecast so clearly.
From the steps of the apartment, children can be heard laughing as they play at a neighbouring school.
