TRIAL: Sketches of a killer

For the very first time, Howell, 51, nonchalantly drew the diagrams of the scenes of the two murders during a police interview in Coleraine Police Station on January 31 2009 - two days after he was arrested.

Questioned by detective constables Alan Devine and Anne Henry, the father of ten drew two floor plans - one of his home at Knocklayde Park and the other of the Buchanan’s house at Charnwood Park, Mountsandel.

The dentist is currently serving 21 years in Maghaberry Prison for killing his wife and mother of four Lesley and pc Trevor Buchanan on the evening of May 18, 1991.

He used a garden hose which he fitted to the family car with son Jonathan’s baby bottle to suffocate Lesley as she slept. Earlier that day the family had celebrated their son Daniel’s second birthday.

Lesley had gone for a hair appointment in the morning and then came back home, made tea and even prepared Sunday’s dinner.

In the first drawing Howell depicts how he unwound the hose from the family car in the garage and led it through the utility room and kitchen into the living room at his Knocklayde Park home.

He points out the couch where defenceless Lesley was sleeping as their four children - Matthew, 6, Lauren 4, Daniel 2 and Jonathan, then just a few months old - lay in their beds just yards away.

In the previous days Lesley - who had begun to drink heavily and take prescribed sleeping pills - had fallen into a deep depression after her father Harry had collapsed and died suddenly in the family kitchen just 12 days previously.

As the toxic car fumes filled the room she stirred but Howell ran in and mercilessly pinned her down with his knees until she was overcome by carbon monoxide poison and took her last desperate breaths.

In the more detailed second drawing, Howell again demonstrates how he wound the garden hose from his Renault Savannah car - with his wife Lesley already dead in the boot - into the Buchanan’s home at Charnwood Park.

He details the route from the garage, utility room and kitchen to the bedroom where he overcame and killed Trevor Buchanan after a brief but fatal struggle.

He also points out how the Buchanan’s car was parked at the front of the house to allow him to reverse his vehicle into the garage.

The drawing shows the location of the fire where his lover Hazel Stewart cut up the hose and burnt it. The ‘Ronnie’ referred to is the next door neighbour and the figure six denotes the size of the garden fence.

Howell carried out the murder as constable Buchanan’s children, Lisa and Andrew, lay sleeping close by in their beds.

Their mother Hazel Stewart told police that she hid away in another bedroom while the killing was carried out and later saw her husband lying dead in the hallway.

A short time later Howell - who says he was almost overcome with the fumes himself and had to run to the bottom of the garden to catch his breath - drove away with the his two defenceless victims to stage the fake suicide at Castlerock.