Howell and Stewart Timeline
BBC News Online looks at the timeline of events which led to the sentencing of Colin Howell and his former lover, Hazel Stewart for the murders of their respective wife and husband.
2 March 2011
At 1047 GMT the judge sends the jury of nine men and three women out at Coleraine Crown Court to consider the verdict.
It takes them just over two hours to find her guilty.
Her former lover Colin Howell pleaded guilty to the murders in November 2010. He was sentenced to 21 years for the murders of Trevor Buchanan, 32, and his wife, Lesley Howell, 31.
1 March 2011
On the 14th day of the trial it is Hazel Stewart's Birthday, she is 48.
The judge begins his summing up in the case.
Judge Anthony Hart acknowledged there had been a lot of public attention on the case and the jury had to put that aside and make their decision based on the evidence.
Mr Hart told the jury the key question was: "Were they in it together?"
28 February 2011
Prosecution and defence lawyers give their closing arguments in the trial.
Mrs Stewart's defence lawyer tells the court she could not have been in a joint enterprise with Howell who regarded her as "weak, vulnerable and easy to control".
The lawyer also says financial issues had motivated Colin Howell to murder his wife Lesley and Stewart's husband Trevor Buchanan in May 1991.
Earlier in the day a prosecution lawyer claimed Stewart agreed to a plan to carry out the two murders so she and Howell could continue their relationship.
He says she helped execute a plan to sacrifice the life of her husband and kill her then lover's wife with carbon monoxide fumes.
24 February 2011
On the 12th day of her trial, Hazel Stewart's defence lawyer tells Coleraine Crown Court that she will not give evidence at her trial.
Earlier in the trial, police interview tapes were played in which Mrs Stewart admits she was aware of a plan to kill her husband but insisted she wanted no part in it.
23 February 2011
The court is played more tapes of a police interview with Hazel Stewart.
In them she cries bitterly and says: "The biggest mistake of my life was ever meeting Colin Howell and I have paid the price,"
"I would like to say sorry to Trevor's family. I can't imagine what it would be like to lose a son.
"I have a son and I love him very much. To David, my husband I love so much. Lisa and Andrew. They are my life and I have lost it."
In another tape played to the court Stewart admits she was part of a plan to kill her husband but insisted she wanted no part in it.
The court hears Stewart tell police how she got rid of evidence.
They also hear how she encouraged her husband to take a sleeping tablet on the night of the murders.
22 February 2011
Through police interview tapes the court hears Stewart describe how Howell often gave her laughing gas.
She says she "went crazy" when she feared her former lover gave her too much laughing gas before they had sex on his dentist's chair.
"I knew what he was trying to do and I freaked out," she says.
21 February 2011
The jury listen to the first of 15 taped interviews Hazel Stewart gave to investigating officers in 2009.
In them she says she wished she was dead when they questioned her about the murders.
At one stage, her daughter Lisa, who is sat in the public gallery beside her brother Andrew, wipes her eyes with a handkerchief.
17 February 2011
On his final day of giving evidence for the prosecution in the trial of his former mistress, Howell denies he was a monster and says Hazel had gone along with the plan.
Howell, tells the court: "It could not have happened without her co-operation, she didn't say no, there was no objection to me being there."
16 February 2011
Money was the only reason Colin Howell murdered his wife Lesley, a lawyer for his former partner claims on the third day of her double murder trial.
The barrister says that the dentist gained £414,000 from his wife's will, life insurance, an endowment payment and cash from her late father's estate.
Paul Ramsey QC, defending Hazel Stewart, put it to Howell, that all his financial problems had been solved with the death of his wife.
But the dentist denies the suggestion, claiming he received only £212,000 as a result of his wife's death.
On the same day Howell admits flicking his wife with live cable a month before her death.
A friend of Lesley Howell, tells the court Mrs Howell had told her of the incident before her death.
14 February 2011
Howell begins giving four days of evidence at the trial of his former lover, Hazel Stewart.
He says Mrs Stewart was not convinced they could get away with making Trevor Buchanan and Lesley Howell's deaths look like suicide.
"I remember the word crazy being used by her," he said.
"That was nature of the objection Hazel gave to me."
Howell says her concern is over being caught, not about the concept
It was the first time some of the details of Howell's role in the murder emerged as Howell pled guilty ahead of his trial.
8 February 2011
The prosecution lawyer says the double murder plot was a joint plan.
He says she played an active role in a joint plan to kill for "selfish ends", as he outlined the prosecution case against Mrs Stewart.
"Hazel Stewart knowingly entered into this agreement and assisted Colin Howell in ensuring he could safely kill her husband and afterwards they both covered up the whole thing," he said.
The prosecution tell the jury about a series of interviews given by Mrs Stewart when she was arrested in January 2009, they say she changed her account of events three times.
7 February 2011
The jury is sworn in for the trial of Hazel Stewart at Coleraine Crown Court.
3 December 2010
Former dentist, Howell is sentenced to a minimum term of 21 years. He is already on remand at Maghaberry Prison.
18 November 2010
Days before his trial is due to begin at Belfast Crown Court, Howell changes his plea and pleads guilty to the murder of his first wife, Lesley and his former lover's husband, Trevor Buchanan.
4 October 2010
Howell pleads guilty to indecently assaulting three women patients at his surgery on dates between July and December 2008. He denies 14 other charges of indecent assault against the same three women and three others.
5 July 2010
Howell is charged with 17 counts of indecently assaulting six women at his dental practice over a 10-year period from 1998 to 2008.
Howell's second wife, Kyle files for divorce and returns to America with her seven children.
Colin Howell and Hazel Stewart are charged with the murders of their former partners, Trevor Buchanan, 32, and Lesley Howell, 31. At the time both deny the charges.
Howell hands himself in a police station almost 20 years after the killings. He admits to police that he gassed his former wife, Lesley and Trevor Buchanan and had fooled police into believing they had taken their own lives.
Howell's eldest son by his first wife Lesley, dies aged 22, in an accident in Russia.
Matthew Howell lost his grip on a stairwell and fell four floors from an apartment block onto a concrete surface below.
He was studying at St Andrews University and was on placement in St Petersburg as part of his undergraduate language course when he died.
Colin meet his second wife Kyle Howell at a bible study class.
She was divorced with two children and had fled an abusive marriage in America before moving to Northern Ireland.
They marry in May and went on to have a further five children.
Howell proposes to Hazel in 1995 and the pair visit two dentistry practices in Scotland with a view to resettling both their families across the Irish Sea but their relationship again ends in 1996.
At first their rekindled romance was a secret but by 1994 Howell took his children round to Hazel's house.
They couple go on family holidays with their children to Newcastle, County Down and the Lake District in England.
A coroner's court rules that both Trevor and Lesley had committed suicide in an apparent pact.
According to medical evidence both died from carbon monoxide poisoning.
In 2009 Howell tells police he had concocted a story to give the impression that his wife and Mr Buchanan had committed suicide because they had struggled to cope after discovering he and Hazel had been having an affair.
Sunday 19 May 1991
Howell contacts church elders to say his wife is missing.
Their bodies are discovered in a fume-filled car in a garage at Lesley's father's house on 19 May.
Hazel Stewart continued to meet Colin Howell in secret after the funerals and continued to do so for up to five years after the killings.
Saturday 18 May 1991
Howell connects a hose to his car exhaust and runs the hose into the lounge where his wife, Lesley is drugged and asleep on the sofa.
He later confesses to police that his wife, Lesley, cried "Matthew", the name of their eldest son, as he held a gas pipe to her face.
Howell calls Stewart to let her know he has killed his wife and is on his way round. He puts his wife's body into the boot of his car and drives to Trevor Buchanan's house.
The police officer struggles briefly after he awakes to find Howell gassing him. Trevor's body is then dressed by Howell and put into the boot of his car along with Howell's wife, Lesley.
Howell drives the car containing the bodies to Lesley's father's house in Castlerock.
He puts Mr Buchanan's body into the drivers seat and places his wife's body outside the boot surrounded by family photographs and a letter his wife had written after an attempted suicide.
7 May 1991
Lesley Howell is left devastated after her father dies. Harry Clarke collapses and dies at his daughter's house.
This was key as Howell later uses his wife's grieving as part of his plan to cover up the murders.
He says his wife was so upset about her father's death and her husband's adultery that she took her own life.
Howell meets Hazel at least twice before the murders to prepare. Once to explain the plan and a second time for Howell to give Hazel sedatives for her to use on her husband, Trevor.
During swimming lessons organised by the church Mrs Buchanan and Mr Howell become attracted to each other.
Hazel became pregnant, and unsure who was the father of her baby, decides to have an abortion. Hazel and Colin travel to England for the procedure.
Following the abortion their relationship ends but resumes several months later.
The couple would meet at Castleroe Forest but were soon spotted by a member of the church.
Both confessed to their partners and pastor. Lesley Howell, who had just had her fourth child takes an overdose. Lesley leaves a note which will become central to the murder cover up.
Trevor Buchanan was left devastated but wanted his marriage to work.
For four months the two couples receive counselling through the church but the affair resumes.
Howell describes their attraction as being "like an addiction".
Colin Howell and Hazel Stewart begin an adulterous relationship. They are confronted by the minister of Coleraine Baptist Church, Pastor John Hansford, about the affair and they agree to counselling.
Hazel and Trevor Buchanan move to Coleraine with their two young children and settle in Charnwood Park.
They attend Coleraine Baptist church where Hazel Buchanan meets Colin Howell at the playgroup.
16 June 1983
Recently qualified dentist, Colin Howell marries young nurse, Lesley Clarke.
They began dating in 1981 after meeting in Belfast and go on to have four children: Matthew, Lauren, Daniel and Jonathan.
The couple are committed Christians and become very active in Coleraine Baptist Church.
11 July 1981
18-year-old farmers daughter, Hazel Elkin, marries RUC Constable Trevor Buchanan, 22, at Omagh Baptist Church.
The Buchanans have two children, Lisa and David, soon after they are married.