Weatherston, a former University of Otago tutor, has been found guilty of murdering his former girlfriend Miss Elliott in a frenzied attack during which he stabbed her 216 times in her Dunedin bedroom.
Grieving parents Lesley and Gil Elliott, and the brothers of the murdered Dunedin 22-year-old, said they were relieved there had been "some justice for Sophie" but the verdict did not bring her back.
Lesley Elliott said the trial had brought all the horror of the last 18 months back again.
"I wouldn't wish this on any other family."
Mrs Elliott said "the public face is different from the private face - it's been tough".
She said she found listening to Weatherston giving evidence very hard and also struggled with the fact she could not rebut a lot of what was said by the defence in the trial.
"I know what went on in that room."
The family also found it offensive that parts of Ms Elliott's diaries had been read to the court.
"They were her private thoughts. They were her privacy and I think for anyone who writes diaries you don't actually want anybody to read them. And we found that really offensive.
The family would now become part of an effort to have the "totally unneccessary" provocation defence repealed, Mr Elliott said.
The family now looked forward to the sentencing and after that could move to get on with their lives, he said.
The Weatherston family said in a statement read by Roger Weatherston they still loved their son.
They were shocked at what he did and now had some understanding of how the terrible event had come about.
They were sad they had not recognised Clayton had needed help and hoped he would now receive it.
They extended their thoughts to the Elliott family.
Weatherston was impassive in the dock as the High Court jury in Christchurch delivered its verdict this morning. He was remanded in custody and will be sentenced on September 15.
Sophie Elliott's mother Lesley Elliott cried quietly. The Weatherston family showed no signs of emotion.
Mrs Elliott and Weatherston's mother embraced inside the court. Mrs Elliott and defence counsel Judith Ablett-Kerr also embraced.
The Weatherston family released a statement saying that what Weatherston had done "came as a great shock and we hope he gets the help he needs in prison".
Weatherston (33), a former economics tutor, admitted stabbing Miss Elliott on January 9 last year but said he was provoked. He had denied murder but admitted manslaughter.
Miss Elliott (22) was a star University of Otago economics student who was about to leave Dunedin the next day to start a job with Treasury in Wellington.
The court over the past four weeks has heard Weatherston and Elliott had a highly unstable and volatile relationship. Her mother told the court she had been concerned about the relationship initially because Weatherston was one of her daughter's teachers.
After locking the door he attacked her, inflicting numerous stabbing and cutting wounds, and seven blunt-force injuries.
A pathologist called by the Crown said the pattern of the 216 wounds indicated "a persistent, focused and determined attack".
The jury was told it was "no coincidence" some of the clusters of wounds related to areas of Sophie's beauty and attractiveness.
Her ears and the tip of her nose had been cut off. There were stabbing or cutting wounds to her eyes, her throat, a breast, her genital area and other parts of her body.
Several pieces of her long hair had been cut.
Weatherston had admitted to the first police officer who spoke to him that he had killed Miss Elliott and had done so because of "the emotional pain she has caused me over the past year".
When he told the officer this, he was speaking in a calm and normal tone.
