Former Brisbane real estate agent Gerard Baden-Clay has been given a life sentence for murdering his wife Allison in April 2012.

A Supreme Court jury on Tuesday found the 43-year-old guilty of murdering the mother of three at their Brookfield home and disposing of her body under the Kholo Creek Bridge, more than 13 kilometres away.

Baden-Clay, who had protested his innocence in the witness box, faces a non-parole period of 15 years.

Allison's family shouted "yes" as the verdict was read out, while security asked for a short break because Baden-Clay was struggling to breathe.

He remained silent when asked if he had anything to say, and shook as victim impact statements were read to the court.

Allison's mother, Priscilla Dickie, said Baden-Clay had "betrayed" her daughter and sentenced his own daughters to a life's journey without a mother

"We have all been robbed of Allison's love. The discovery of our darling daughter was absolutely devastating," she said.

"The tragedy of it all is she had so much to offer."

Allison's father Geoff Dickie told the court he had been left "devastated by the murder of my precious, gifted and talented daughter".

"Our lives will never be the same until the day I die," he told the court.

"It's a father's job to protect their daughter - I have failed in that."

Allison's sister Vanessa Fowler said her sister was a "strong woman" and the court had been told "terrible lies" during the trial, which heard evidence she suffered debilitating bouts of depression.

"My sister today, for the first time since she married you, has come out on top," she said.

In sentencing, Justice John Byrne said Allison's death was not premeditated but was "violent".

"The prosecution suggested that you smothered Allison, and that looks likely," he said.

"But whatever the mechanism, your violent attack caused her death.

"Her fingernails scratched your face - the act of a desperate woman struggling for life. Those marks are only consistent with your guilt.

"Your shameful conduct after murdering Allison bespeaks a profound absence of remorse."

'We didn't get a chance to say goodbye'

Outside court, Allison's best friend Kerry-Anne Walker spoke on behalf of Allison's family and supporters, saying Baden-Clay's jailing will allow them to "mourn and grieve this beautiful woman".

"Today is a not a win for our family, because it will not bring our beautiful Allison back. However, it is the closure of another chapter in this journey for our family," she said.

Sorry, this video has expired Gerard Baden-Clay returns to prison after being handed a life sentence

"Our primary concern has always been and remains the emotional and physical well-being of Allison's beautiful girls.

"We have a long way to go to ensure that they will cope with a future without their mother.

"We, her family and friends, didn't get a chance to say goodbye, but Allison will always remain forever in our hearts."

It was a case about sex, lies and murder that gripped the city of Brisbane for two years, and the ever-growing queues outside the Supreme Court were a testament to the public's fascination with the sordid story.

In life, Allison Baden-Clay was a dancer, teacher, successful career woman, devoted wife and mother of three girls.

In death, she became well-known for all the wrong reasons.

Her disappearance in 2012 shocked the tight-knit affluent community of Brookfield. Well-wishers and concerned residents laid flowers at her home, not knowing what else to do.

At the same time, hundreds of police and State Emergency Service (SES) volunteers swung into action, combing surrounding suburbs for any trace of the missing woman.

"Please help us, because there are three beautiful little girls of Allison's wanting to see their mother," her father had pleaded.

Her mother urged: "Our lives will never be the same - we must, must find her - she's so precious."

Allison Baden-Clay's parents, Geoff and Priscilla Dickie, stand behind Allison's good friend Kerry-Anne Walker outside court. ( AAP: Dan Peled )

Premier vowed resources to find Allison

Queensland Premier Campbell Newman vowed to commit whatever resources were necessary to finding her.

"I'm just very sad for the family and friends. It's obviously just incredibly distressing," he said at the time.

However, from the moment Baden-Clay reported his wife missing on April 20, 2012, police knew this was no ordinary missing persons case.

He had told them she went for an early morning walk and never returned home.

But marks on his face alerted police that something more sinister may have happened.

Hours turned into days, and on April 30 a lone kayaker discovered what was later confirmed as Allison's body on the muddy banks of Kholo Creek at Anstead, about 10 kilometres from the family's home.

That day, police refused to say whether Baden-Clay was a suspect.

On June 13, however, he was arrested and charged with his wife's murder.

After the verdict, Detective Superintendent Mark Ainsworth thanked SES volunteers, the Brookfield community and Allison's family for their assistance throughout the police investigation and searching for Allison in the days after her disappearance.

He said police officers "never waivered" during the massive police investigation, which comprised six divisions of Queensland Police and more than 60 detectives following up more than 1,500 lines of inquiry.

"One disappointment out of this investigation, if anything, was the time it took us to find Allison," he said.

Flowers and toys decorate a memorial for Allison near the Kholo Creek location where her body was found in Brisbane's west, June 23, 2014. ( AAP: Dan Peled )

Crown case against Baden-Clay circumstantial

By its own admission, the crown's case against Baden-Clay was a circumstantial one, but the accumulation of evidence was powerful.

A post-mortem examination failed to determine a cause of death due to decomposition, and apart from a chipped tooth and possible bruising, there were no fractures to Allison's body.

Marks on the face of Gerard Baden-Clay. ( Supplied )

But forensic pathologist Dr Nathan Milne believed Allison did not die from natural causes.

The crown said she died at the hands of her husband, the last person to see her alive.

At the time of her disappearance, Baden-Clay had marks on his face and body that drew the attention of police.

He had excuses for them, though: he had cut himself shaving in a rush; the marks on his neck were where he had crushed a caterpillar that had landed on him while he was watching one of his daughters compete in a cross-country race; and marks on his hand were from a screwdriver that slipped while he was helping renovate a friend's house, but marks on his chest and shoulder could not be explained by him.

However, three forensic experts testified that marks on Baden-Clay's face were likely fingernail scratches and Baden-Clay's claim that they were from a razor was simply implausible.

They said marks on Baden-Clay's body could also be from scratching, although they were less conclusive.

Then there was the dripping blood found in the boot of Allison's four-wheel drive. DNA testing confirmed it was Allison's.

Baden-Clay's double life

The murder trial exposed a couple living very different lives publicly and in private.

On the face of it, the Baden-Clays were a successful family, running their own prestige real estate company.

But they were in deep financial trouble and Baden-Clay was having trouble paying off loans to friends.

In desperation, he had begged the state Member for Moggill, Dr Bruce Flegg, for a loan of up to $400,000, fearing he would go bankrupt without it.

Baden-Clay was also caught between two women: his wife and lover.

In marriage counselling, Baden-Clay had professed to want a future with Allison, but at the same time was vowing to leave his wife on her birthday for former employee Toni McHugh.

An email trail between Ms McHugh and a secret account set up by Baden-Clay under the name Bruce Overland portrayed a tumultuous affair, and growing frustrations from Ms McHugh about her lover's unfulfilled promises.

"Well you'll have to forgive me that I feel disappointed when this happens. I'm sick of hiding," Ms McHugh wrote on February 20, 2012.

"I'm sick of being second best and having to take the back seat ... all so she doesn't find out.

"Why should I believe things are going to be any different than the past[?]"

Ms McHugh wrote on March 27 she had looked at rental properties.

"It would be so much easier if you did just move in with me," she said.

"She can get her own place and the week you have the children you move back to the house."

Baden-Clay wrote on April 3: "I have given you a commitment and I intend to stick to it - I will be separated by 1 July."

He also wrote an email on April 11 - referring to Ms McHugh as GG - their names for each other were Gorgeous Girl and Gorgeous Boy.

"This is agony for me too. I love you," he said.

"I'm sorry you hung up on me. It sounded like you were getting very angry. I love you GG. Leave things to me now. I love you. GB."

Until April 2012, Baden-Clay had been able to keep his two worlds separate, but they were about to collide spectacularly.

On April 20, Allison and Ms McHugh were due to attend the same real estate conference.

(LtoR) Allison Baden-Clay, Gerard Baden-Clay and Toni McHugh. ( Supplied/AAP )

In the witness box, Baden-Clay passed off his declarations of love to Ms McHugh as empty promises to appease a volatile, unstable and confrontational woman who was infatuated with him.

He portrayed himself as a philanderer, but no murderer: he had affairs with numerous women, but was never going to leave his wife.

Baden-Clay admitted he deceived Allison, Ms McHugh, his family and friends, and in return for his deception they gave him their loyalty.

"My intention was to end any relationship with Toni McHugh and solidify and continue my relationship with Allison for our future together," he said in the witness box.

But the crown submitted Baden-Clay and Ms McHugh were very much entwined and his deceptive conduct showed what he was capable of.

Allison's mental health raised at trial

The jury saw two faces of Allison. The defence painted a picture of a woman plagued by depression and unable to cope with the pressures of life.

Analysis: Surprise at guilty verdict Queensland law expert Associate Professor Heather Douglas has followed the trial closely and says she found the jury's guilty verdict "a bit surprising". "It was mainly circumstantial evidence that, well almost entirely circumstantial evidence, that the jury was faced with," she told The World Today. "It's an unusual situation because Baden-Clay was a very articulate person, well-dressed and from the right side of town if you like, so I guess I was a bit surprised." Listen to the full story.

They pursued the possibility that Allison could have taken her own life or wandered off into the night to her death.

According to testimony from Baden-Clay's father, Nigel, and sister Olivia Baden-Walton, Allison was so incapacitated she could not get off the couch.

But her friends and family told a different story: she was a woman who was happy and feeling positive before she disappeared.

A GP, two psychologists and a psychiatrist who had treated Allison all said she was not a suicide risk.

Marriage counsellor Carmel Ritchie, who consulted with the couple just days before her death, also testified that Allison was hopeful for her future and wanting to make her marriage work.

One thing was clear, however: their marriage was in crisis. Allison's journal revealed a woman tormented by self-doubt.

Sorry, this video has expired Chapter closed on case that gripped Queensland ( Francene Norton )

"I don't want to be alone," she wrote.

"I am afraid of being alone and lonely, maybe because I think I can't handle it. I am afraid of failing - failing in my marriage and what people will think."

Allison also had lingering questions about her husband's affair with Ms McHugh. Some were answered, some were not.

Questions like how many times did they go to the movies together? How did they pay for hotels? Where did they have sex in her apartment? Sex in the family car?

"Did she ever say: 'I feel bad because you're married?'"

Three daughters left behind

The trial was the first time the public had heard the three Baden-Clay children speak about their mother's disappearance.

Heartbreaking video recordings of police interviews with the girls, then aged 10, eight and five, taken on the afternoon their mother was reported missing showed their fear, distress and confusion at what was happening around them.

Baden-Clay wiped away tears while watching his daughters sob as they were quizzed by detectives.

Each described being put to bed by their parents. The middle girl remembered her mother singing Away In A Manger to her.

"Dad said mum had gone for a walk," the eight-year-old said.

The youngest child said: "She was walking for a long time and we think she twisted her ankle.

"I didn't get to see her at all because I was fast asleep."

The eldest recalled seeing her mum on the couch watching TV when she got up to get a glass of water.

"Dad was trying to keep calm for us, but I don't actually know what was going on in his head," she said.

She saw "scratches" on her dad's face, but none of the girls heard anything during the night.

The families and supporters of the Baden-Clays have sat through each day of the trial listening to evidence almost too painful to bear.

They are bound by grief, but divided by loyalty.

The guilty verdict gives them an answer - wanted or not.

But one question remains, and only Baden-Clay can really answer how he murdered his wife.

Amidst the murky personal drama are three little girls who lost their mother and will now have to learn to live without their father.

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