Killer dentist Colin Howell won’t be charged for any sexual offences against Hazel Stewart

The Public Prosecution Service took the decision after reviewing claims that he sedated and subjected her to serious assaults.

It represents a blow for any attempt by 58-year-old Stewart to mount a fresh appeal over her own conviction for double murder.

Her lawyers confirmed they are seeking an immediate review of the decision.

The former Sunday School teacher is serving at least 18 years behind bars for her role in killing her police officer husband and Howell’s wife.

The bodies of Lesley Howell, 31, and Constable Trevor Buchanan, 32, were found in a fume-filled garage in Castlerock, Co Londonderry in May 1991.

Police originally believed they had died in a suicide pact after discovering their partners were having an affair.

Nearly two decades passed before Howell, 61, suddenly confessed to both murders.

He pleaded guilty in 2010 and was given a minimum 21-year sentence. He implicated Stewart in the plot and went on to give evidence against her at her trial.

Howell is also serving a separate sentence for sexually assaulting five female patients while they were under sedation at his dental surgery in Ballymoney, Co Antrim.

He committed those offences over a 10-year period from 1998 and 2008.

In April 2018 detectives questioned him about further alleged historical sexual assaults and sent a file to the PPS.

Stewart’s lawyers later confirmed she was the complainant and had waived her right to anonymity.

Since being convicted she has failed in a series of attempts to have the verdicts overturned.

If Howell had been charged and ultimately found guilty of sexually assaulting her, it could have opened up a potential new ground of appeal, based on claims that she was at all times under his control.

Instead, however, a decision has been taken not to prosecute.

In a letter to Stewart’s legal representatives, the PPS said it has concluded there is insufficient evidence for a reasonable prospect of obtaining a conviction.

Her solicitor, Kevin Winters, confirmed she is contesting the reasons for the no prosecution direction.

“Firstly, she rejects absolutely the suggestion made by Howell that she consented to sedation for the purposes of sexual activity,” he said.

“Secondly she asserts that at all times she has been consistent in her allegations made to police.”

Mr Winters added: “Our client is concerned that the decision not to prosecute may have been motivated to block any future application by her to challenge her double murder conviction.

“We have asked the PPS to review this decision immediately and expect to receive confirmation details on the Review process as soon as possible.”

In a statement the PPS confirmed a decision was issued today not to prosecute one individual reported by police in connection with allegations of sexual assault dating back to the early 1990s.

A spokesperson said: “These decisions were taken by an experienced Senior Public Prosecutor.

“After careful consideration of all the available evidence, it was concluded that there was insufficient evidence to provide a reasonable prospect of conviction for any offence.

“All decisions were taken fully in line with the PPS’s Code for Prosecutors.

“We have written to all relevant parties including the complainant to explain the reasons for these decisions.

“We have also offered to meet with the complainant to explain the reasons in further detail if they wish.”

The spokesperson added: “Speaking generally, the PPS is fully committed to prosecuting sexual offences robustly when there is the evidence to do so.”