John Barrie Wilby, 70, is the son of Vera Wilby, who was poisoned in 2002 by Norris - notoriously labelled the Angel of Death - while working at Leeds General Infirmary and the city’s St James’s Hospital in 2002.
Norris, now 40, was found guilty at his trial of the attempted murder of his patient Mrs Wilby, along with the murders of Doris Ludlam, 80, Ethel Hall, 86, Bridget Bourke, 88, and Irene Crookes, 79.
But on Monday, a BBC Scotland documentary, The Innocent Serial Killer?, claimed advances in science has cast fresh doubt on the conviction.
The programme raised the possibility that all of Norris’s victims could have died from natural causes, quoting Professor Terry Wilkin, an endocrinologist specialising in diabetes at the University of Exeter, who questioned the blood test on Ethel Hall.
Mrs Wilby’s only son, retired chartered surveyor Mr Wilby, who lives in Reading, said: “I sat through the trial and listened to the evidence. I came to my own conclusion then that he did do it.
“We had visited my mother in hospital the weekend before her operation and then the weekend after. I saw that she had gone from an independent lady to someone who was catatonic, she was incoherent, it was a remarkable change. The difference was dramatic.
“At the time, doctors could not explain why my late mother had become hypoglycaemic, but if you look at the programme last night they say this can happen to between five and 10 per cent of elderly patients following an operation - if this was the case then surely this should have been happening since operations began.
“The programme said it is common but doctors at the time were at a loss to explain what had happened. It seems odd to me and doesn’t add up. I found it difficult to believe. My mum was at a teaching hospital, and what was happening was outside their experience.
“I’m still convinced of Norris’ guilt.
“It is the common sense approach. What was shown on television last night was a one-sided view. It was a belated admission of evidence for the defence.
“The jury at the time were presented with varied amounts of evidence and they came up with their guilty verdict.”
He continued: “A year after my mum died we were starting to come to terms with her death when we discovered police were investigating her death and from then on her memory has been tarnished.
“We’ve had to continually look back at that difficult last year of my mum’s life for almost 12 years now, when we should have been thinking of her in terms of the wonderful caring woman she was, everything a mother should be.
“But things such as this keep being brought up and there is no end to it, there is no end to the bereavement I feel for my mother.
“You start to get over it and the it’s like a scab on a sore, it comes off and it’s hurting all over again.
“Any relative attached to this is of course feeling sad and angry about it being brought up again.
“I do believe what is the driving force behind all this is Norris’ own mother, who cannot accept his guilt.”
Vera Wilby had been admitted to hospital for a routine hip operation after she fell as she was on her way to vote at the polling station in the local elections in May 2002.
She was poisoned by Norris and deteriorated badly.
She did survive the “attack” (as Mr Wilby calls it) but she never regained her full health and ended up in a convalescence hospital and then in a nursing home in Ilkley, until her death from an infection in January 2003.
“When Norris was found guilty it was a satisfactory conclusion. But it actually never ends,” her son added.
“I met Norris on the ward a couple of times and I found his manner to be abrupt. He was very offhand and uncaring.
“Of course I didn’t consider he could be a murderer but when the police told me he was a suspect in my mother’s death it didn’t surprise me entirely.
“He came across as an oddball during the trial, sometimes he would turn his back to the jury and he seemed very ill at ease with himself.”
Glasgow-born Colin Norris, 40, was jailed for life in March 2008 for killing Doris Ludlam, 80, Ethel Hall, 86, Bridget Bourke, 88, and Irene Crookes, 79, and attempting to murder Mrs Wilby, 90, while he worked at Leeds General Infirmary and St James’s Hospital in 2002.
A jury found him guilty of the crimes after being told he had injected them with lethal doses of insulin.
But Norris has always protested his innocence and denied injecting patients.
West Yorkshire Police said: “Norris was arrested, prosecuted and, on the basis of the evidence presented to the court, he was convicted and sentenced.
“His conviction was upheld at the Court of Appeal in December 2009. The case is currently under review by the Criminal Cases Review Commission (CCRC) and we will consider their findings when they are presented to us.’
The BBC said it was making its evidence available to the CCRC.