His family today made an appeal for information which they believe could prove someone else committed the crime at the couple's Kidderminster home.
Evans – who admits he had an affair but still denies any attack on his wife Louise – is gearing up to lodge an appeal against his conviction and the sentence that condemned him to spend at least 17 years behind bars.
His parents, sisters and brother, who have complete faith that he is innocent, are desperate for more information about an anonymous letter sent to police in August last year, which claimed a man named 'Gareth' had confessed to killing Louise.
Sue Evans said: "My son has been labelled a murderer and a monster – and he is neither. His only crime is having an affair."
The hunt for the writer of the anonymous letter – or the person named as the possible culprit – is a race against time because an appeal needs to be lodged within 28 days of Evans's sentencing on November 6.
A jury at Worcester Crown Court found Evans, a 35-year-old welder, guilty of murdering Louise, aged 32, the mother of their three young daughters, at their home in Stoney Lane, on July 10 last year. Louise was found dead at the bottom of the stairs and the jury believed that Evans punched her and pushed her during a row about his affair with teaching assistant Amanda Chadwick.
The prosecution alleged that Evans must then have smothered Louise to death.
But his defence was that he had never attacked his wife in the 18 years since they got together as teenage sweethearts and that her death must have been an accident.
Still reeling from the shock of the verdict almost two weeks later, Mrs Evans, aged 59, said at her home in Bewdley Road North, Stourport: "We as a family – and his friends – know that Alan hasn't done this. He's been sentenced for a crime he has definitely not committed."
Evans's father, 63-year-old Keith, said: "Our son lied repeatedly about having an affair – we've all slammed him for that. But that's what people do when they have affairs."
Sister Tina Price, aged 32, of Garland Road, Stourport, said: "We all loved Lou and want to know why she died because we want justice for her. But what has happened is not justice for either Lou or Alan."
His other sister, Kim Evans, aged 30, of Severnside Mill, Bewdley, said: "If Alan had hurt Louise, we wouldn't have been protecting him - we adored her."
At the trial, the jury was told that Evans put a skipping rope under his wife's body and a vacuum cleaner at the top of the stairs to make it look as though she tripped and fell.
After the verdict, Detective Inspector Dean Jones said: "Evans was a manipulative character who would do whatever it took to mislead the investigation."
And Louise's mother, Judy Bollen, spoke of how her family's 'happy world' was shattered for ever after she was murdered by her cheating husband.
But Evans's family paints a very different picture of him.
They say that, every month since Louise died 16 months ago, he has written a letter, addressed to her 'in heaven' apologising for having an affair.
Sue Evans says that, when the jury at Worcester Crown Court gave its 'guilty' verdict, it felt 'like someone had put a noose round our neck'.
"We never dreamed the jury could find him guilty - the evidence against him was purely circumstantial," said Mrs Evans who is a carer for older people with dementia in the community.
Both his parents and his two sisters have spoken of their agony after his conviction, which has led to a rift that means they can no longer see his three young daughters - their grandchildren and nieces - who are now being brought up by Louise's parents, Derek and Judy Bollen.
An emotional statement from Mrs Bollen, read to the court, asked how they could tell three little girls that their daddy murdered their mother.
"Because of Alan, we have lost our daughter," she said.
But Evans continues to protest his innocence, claiming he never laid a finger on Louise in their 18 years together - and saying his only 'crime' was to have an affair with Amanda Chadwick, who worked at their children's Kidderminster school.
Having told the court that he and Louise were trying to patch up their marriage after the end of the four-month affair, he also admitted that he resumed his relationship with Ms Chadwick after his wife's death.
Although they strongly disapprove of it, the Evans family says he would have been 'stupid' to do that if he was guilty of murder.
Now Evans still pens those letters to Louise from his cell at Hewell prison, near Redditch.
"He tells her what he did in having an affair was wrong - and he tells her where he is now," said Mrs Evans.
"If Lou could speak to us today, she would tell you how wrong this conviction is."
Mr and Mrs Evans, Tina, Kim and brother Barry, aged 37, who lives in Florida, have launched the appeal for more information about the anonymous letter, which they think could hold the key to clearing Evans.
The letter said that a man, aged about 30, named Gareth, from Kidderminster, had claimed he 'killed that lady down Stoney Lane'.
Police investigated but never tracked down the author of the letter or the person referred to as the killer.
The family is asking anyone with information to contact them urgently at his sister Tina's email address firstname.lastname@example.org, his father's at email@example.com or at a Facebook site launched in support of Evans, called 'I'm Backing Al'.
The family says that they and Evans originally believed that Louise's death was caused when she accidentally fell downstairs.
But they now think there could have been another scenario - that someone could have sneaked into the house while Evans, renowned as a deep sleeper, had a nap downstairs.
They do not know why someone should want to attack Louise but say it could have been a burglar
Kidderminster Police DI Dean Jones said today officers would not comment while a possible appeal was to be launched.