Danai Muhammadi has been found guilty of murdering his estranged wife, their young son and his father-in-law in an arson attack.
The 24-year-old was fuelled by "spite, anger and resentment" when he killed Melissa Crook, 20, and their 15-month-old son Noah by torching the house in Chatham Hill, Chatham, Kent following the collapse of their marriage.
Mrs Crook's father Mark Crook, 49, was left critically ill with severe burns in hospital following the fire just before 2.30am on September 10 last year and he died six days later.
Muhammadi and his friend, bouncer Farhad Mahmud, 35, squirted petrol through the letter box using a garden spray container, leading to fire breaking out at the base of the stairs. Mahmud was also found guilty of three counts of murder.
The two men showed no emotion as they learned they faced life behind bars.
As the sentence was read out a family member shouted "good".
Muhammadi's new girlfriend, jobless Emma Smith, 21, was cleared of three counts of murder and two counts of attempted murder but convicted of three counts of manslaughter after a six-week trial at Maidstone Crown Court.
Muhammadi and Mahmud were also found guilty of two counts of attempted murder.
In the public gallery, survivors Amanda and Bohdan Crook shook visibly and hugged each other as the jury foreman read out the verdicts in front of a packed courtroom.
Speaking after the case, Amanda Crook said: "The verdict today is not a cause for celebration for us, the family, but we are relieved that we have at least received justice.
"The evil people convicted today are now deprived of their liberty, and justly so.
"However, no sentence they received could bring back the loved ones they took from us."
BITTERNESS AND JEALOUSY
Prosecutors said the arson was a "wicked attack" which had been well planned following the breakdown of the marriage between Iraqi-born Muhammadi and Mrs Crook.
Six months earlier, she decided to move out of their home in Coventry after Muhammadi slapped her around the face after she refused to have sex with him one night.
She returned to her parents' home in Chatham with her son, while Muhammadi, of Britannia Street, Coventry, started a relationship with Smith.
However Smith became resentful of her new partner's attempts to patch up his marriage with Mrs Crook, jurors heard.
A series of angry text messages were exchanged between Smith, of Barley Lea, Stoke Aldermoor, Coventry, and Mrs Crook in the days and weeks leading up to the arson, in which Smith taunted her love rival.
She mocked Mrs Crook about her size, for being "boring" in the bedroom and added: "Enjoy your life with no husband, no house...no money, you gold-digger."
Muhammadi travelled from Coventry to Kent with Smith late on September 9, after loading the spray container in the boot of his Renault Megane, and headed to Mahmud's flat in Fernhill Road, Maidstone.
The couple let themselves into his home and partied while Mahmud finished a shift as a doorman at a local nightclub. Within half an hour of returning home, Mahmud and Muhammadi left in the Megane, leaving Smith behind in the flat.
CCTV images, automatic number plate recognition (ANPR) and mobile phone cell site recordings helped place their movements over the next 45 minutes.
At 2.03am, the Megane was caught at a Texaco garage in Chatham where more than £15 worth of petrol was poured into two containers, including the garden sprayer.
Minutes later, the fire was set. Petrol was sprayed about four feet into the three-bedroom terraced house through the letterbox before flames ignited at the base of the stairs.
The position of the fire left no means of escape for Mrs Crook, her mother Amanda, brother Bohdan, father Mark and her 15-month-old son by Muhammadi, Noah.
Mahmud telephoned Smith, who by this time was still at his flat in Maidstone. Seconds after that call finished, she dialled 999 from a pre-paid mobile phone reporting that she had spotted a house on fire.
Moments after she ended that call, she telephoned Muhammadi for 23 seconds, long enough to tell him that she had done what she had been asked to do, according to prosecutors.
'I WATCHED THE WINDOWS MELT'
As the fire ripped through the building, Bohdan jumped out of a front bedroom window, causing fractures to his feet and hands. He then tried to brave the flames and reach his mother inside but she eventually managed to escape.
Meanwhile, Mrs Crook collapsed in an upstairs bedroom and she was found dead by firefighters lying with her young son who was wrapped in a quilt.
Her heavily-built father tried to flee but he was caught by a fireball which erupted as he tried to escape through an upstairs window on to a flat roof outside. He died in hospital six days later.
His widow told the court: "I stood and watched him burn. I saw the windows melt. As Mark came through the window, there was a fireball which blew the windows out and engulfed him.
"She added that the heat was so intense she could hear her hair singe.
COVERING THEIR TRACKS
In an effort to eliminate himself from suspicion, he texted Mrs Crook at around 11am that morning, writing: "Hi mel, hope you both well. Can I book the hotel for 22 September. Let me know please. Love you, mate. Give Noah (a) hug and kiss from me. X."
Prosecutor Mark Dennis QC described it as a "cynical and breathtaking attempt" to protect himself from suspicion of the arson attack he committed just hours earlier.
Around the same time, texts were exchanged between Muhammadi and Mahmud who provided his bank details to apparently receive payment for fulfilling his part of the deal.
Meanwhile, Smith attended a walk-in medical centre later that morning complaining of feeling unwell. She deleted all her text messages from her first phone, and the pre-paid phone she used to dial 999 was disposed of and never traced.
Suspicion fell on Muhammadi quickly after ANPR results emerged showing Muhammadi's Megane had entered Kent from Coventry before the fire started and left soon afterwards.
After he was arrested, police found a Maidstone post-code written on a scrap of paper at his home - and that development led detectives to Mahmud who was also held on suspicion of murder.
In court, Muhammadi's version of events was dismissed by Mr Dennis as "absolute tosh".
After being presented with evidence of him coming into Kent on the night of the arson, he admitted he was there to meet some mystery men who had tried to blackmail him.
He claimed he had received an anonymous hand-written letter threatening his son with kidnap and the burning down of their home or car unless £5,000 was paid to them.
He said the letter-writer told him to take the cash to a rendezvous point at 2pm on September 9 last year - hours before the arson - but that he did not hand any money over.
During his evidence, Muhammadi proclaimed his love for son, calling him his "great love". Breaking down, he said: "He meant everything to me and I was very happy.
"I prayed to God that any harm or disease that came to him be passed on to me, not him." He added that he had a tattoo of Noah etched on his arm, against his religious beliefs.
THOUGHTS OF EXTREME VIOLENCE
It was clear, however, that Muhammadi had thoughts of extreme violence. Up to three months before the fire, he told one workmate he wanted to harm his estranged wife, telling them he was going to throw acid in her face to "f*** up her life".
And he also spoke about setting fire to her house about three weeks before the fatal blaze but the colleague did not take him seriously.
Jurors were told that after spending his childhood in Iran, Muhammadi arrived in the UK in 2005 aged 18 and at first lived in Hull where he worked in a cucumber factory and a chicken factory.
Two years later, he moved to Maidstone and met Mrs Crook when she was then aged 16. The pair moved to Coventry in June 2008 and they married in September the following year.
A date for sentencing was provisionally set for the first week in July, the judge said.
'THREE GENERATIONS LOST'
Detective Chief Inspector David Chewter, from the Kent and Essex Serious Crime Directorate, said: "This was one of the most tragic cases I have dealt with in 24 years of policing and my thoughts are with the Crook family who lost three generations of their close-knit family as a result of the fire which was deliberately set by someone they had welcomed into their family.
"Muhammadi was driven by jealousy and, from day one, has denied his involvement in the death of his wife Melissa, young son Noah and father-in-law Mark.
"The use of data communication technology in the shape of ANPR, CCTV and mobile phone information was key to us being able to quickly arrest him for this terrible crime.
"That evidence has proven to be incontrovertible in court and it is only right that the jury have returned a guilty verdict here today and justice has been done for the Crook family who will be haunted by what happened that night for the rest of their lives."
Steve Griffiths, of Kent Fire and Rescue Service, said: "This was an extremely harrowing incident for our local crews who were at the scene within minutes of being called.
"Despite their best efforts, which should be commended considering the ferocity of the fire, they were unable to save three members of this family and we extend our deepest sympathies to their relatives and the local community.
"Our fire investigation team worked closely with their police colleagues and the ongoing development of this service is demonstrated by the overwhelming and conclusive evidence seen by the court.
"We hope it sends a clear message to others that arson can easily lead to tragedy and is punishable by a considerable jail term."