Stewart is investigated by National Crime Agency

The National Crime Agency has launched High Court proceedings against her in a bid to recover funds she gained following the death of Trevor Buchanan.

Stewart, 50, is serving a minimum 18-year jail sentence for the murders of Constable Buchanan, 32, and 31-year-old Lesley Howell, the wife of her ex-lover Colin Howell.

The civil action, brought under proceeds of crime legislation, is understood to centre on finances which have since been tied up in her family home.

Her second husband, retired police superintendent David Stewart, has been named as a joint respondent.

However, there is no suggestion whatsoever of any wrongdoing on the part of Mr Stewart.

In court last Friday, a judge listed the contested case for a two-day trial next May.

Barrister Eugene McKenna, appearing for both of the Stewarts, told Mr Justice Treacy that legal aid is still being sought.

He added: “It’s not a case where there is an interim receiving order or a property freezing order.”

The move by the National Crime Agency comes as Stewart continues to prepare a second attempt to clear her name.

The former Sunday school teacher’s legal team has sent her case to a body which examines potential miscarriages of justice.

They want the Criminal Cases Review Commission (CCRC) to refer her conviction for the murder of Lesley Howell back to the Court of Appeal.

Separate efforts are also being made to overturn a verdict that she killed Trevor Buchanan as part of the same plot.

Her lawyers intend to introduce fresh psychiatric and psychological evidence.

They also want to raise disclosure issues connected to another potential witness.

Both victims 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.

They were in fact murdered before their bodies were arranged to make it look like they had taken their own lives.

Nearly two decades passed before dentist Howell, 54, suddenly confessed to both killings.

In March 2011 she was unanimously convicted of both killings by a jury at Coleraine Crown Court.

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The Court of Appeal held there was strong evidence that she was a knowing and willing participant in the plan hatched by Howell.

But lawyers now acting for Stewart have formally asked the CCRC to examine her case.

It could take up to two years before the body reaches a decision.

In the meantime Stewart’s legal team are also seeking to take her conviction for murdering Constable Buchanan back to the Court of Appeal.

She insists her challenge to that verdict was never abandoned. Nor was there ever any acceptance of guilt.