He was driving a friend and her two children when the accident occurred last year. One of the children, a 3-year-old, was not secured in a child restraint and was concussed when thrown from the vehicle. A 1-year-old suffered a broken arm and their mother suffered two fractures to her spine.
Debbie Ashton's mother Judy Ashton said yesterday she couldn't get her head around it.
"Yes, he's a concern to me, yes he's a concern to the police, yes he's a convicted criminal, but the same thing is going to keep happening if he is allowed back into the community with a new name, because he can tell people what he wants.
"It's not sitting well with me, I can't believe that a person who is known to have killed one person and hurt another can basically get out and start anew ... I just can't get my head around it.
"People like him will drive regardless of whether they have a licence or not," she said. "A prison sentence is the only thing standing between him and society."
Barclay had previously pleaded guilty to three charges of causing injury while driving under the influence of a controlled drug and a charge of breaching release conditions for the expressway accident.
Judge Tony Adeane sentenced him to two years imprisonment and he was disqualified from obtaining or holding a drivers licence for three years.
Judge Adeane said the court was not allowing him to "expunge" his criminal past but ensuring the witness protection programme measures were effective. He permitted the publication of his previous identity.
Defence lawyer Matthew Phelps said Barclay suffered from bipolar disorder and depression, and struggled with drug addiction.
"The indications were that he was turning things around," he said. "[He] is extremely remorseful for his actions."
Debbie Ashton died in a head-on crash near Nelson in December 2006. Barclay was travelling between 96km/h and 112km/h when he became airborne at the crest of a hill and encroached into the opposite lane.
The speed limit in that area was 60km/h. He had been drinking and was disqualified from driving at the time.