THE prosecution described Colin Howell and Hazel Stewart's murder of their spouses as "a meticulous and devious plan and pre-meditated in a manner that might be described as professional".
Howell (51) killed first his wife Lesley and later Trevor Buchanan at their Co Derry homes in May 1991 when he attached part of his baby's feeding bottle to a garden hose, gassing them with carbon monoxide as they slept.
He and Stewart were reunited during their on/off affair when the murders were carried out late on Saturday night/Sunday morning May 18-19.
His wife, who had been drinking and taking prescription tablets because of her distress over his infidelity, was sleeping on a sofa when he attached the hose to the exhaust of their car and ran it through the house to where she was lying.
Switching on the engine, he waited at the door but Lesley woke up and cried out for her son Matthew (6), sleeping in another room with his sister Lauren (4). Brothers Daniel (2) and Johnny (9 months) were also in the house.
Howell pulled a duvet over her head and pushed the hose into her face, holding it there until she died.
Read more:
- How the murderer's 18 years of deceit, prevarication and depraved self-justification finally ended
- Colin Howell's second wife moved to Florida to free family from his legacy
He dressed her and carried her to the boot of the car, placing a blanket over her head and a bicycle on top of the body, driving from his Knocklayde Park home in Coleraine to the Buchanans' Charnwood Park house where Trevor was asleep in his marital bed.
From the garage he repeated his garden hose trick, placing it close to Mr Buchanan. However, the RUC scenes-of-crime officer woke up too, saw Howell, and a struggle ensued.
Howell trapped his victim's arms inside a quilt and pulled it over his head, shoving the hose towards his face.
Dizzy from the fumes, he left to catch his breath before returning to dress and carry Mr Buchanan to the car boot beside Mrs Howell's body.
As her young children slept, Stewart disposed of the hosepipe and cleaned the room where her husband died.
Leaving his bicycle on a verge to aid his escape later, Howell drove to a row of houses at Cliff Terrace, Castlerock, known as the Twelve Apostles.
One had been owned by Lesley's father, Harry Clarke, who had collapsed and died at his daughter's home 12 days earlier.
In its garage, he pulled on a pair of plastic surgical gloves and placed Mr Buchanan in the driver's seat and Mrs Howell in the boot with family photographs beside her and her personal stereo playing.
Howell connected a length of vacuum hose to the exhaust, with the other end in the boot, switching on the ignition before cycling home.
It had all happened inside the space of four hours.
The following morning he called the police asking if his wife had been in an accident, saying she and Mr Buchanan had left the house together after an argument with him and she had been drinking.
He asked a church elder to go to the Apostles to see if his wife was there, only 'finding' them after returning a second time with an off-duty police officer.
He suggested his wife and Mr Buchanan had taken their own lives because they had struggled to cope after discovering the affair.
Howell was able to pay off debts, including his mortgage and develop his dental practice in Ballymoney with £212,446 left in his wife's will, her father's £27,000 estate and £120,000 life insurance and £54,635 from an endowment policy.
In 2008 he sold a home for 131,000.
Read more:
- How the murderer's 18 years of deceit, prevarication and depraved self-justification finally ended
- Colin Howell's second wife moved to Florida to free family from his legacy
