Margaret Fleming was reported missing in October 2016 from her home in Inverkip, Inverclyde, but it is claimed she has not been seen since December 1999.
Edward Cairney, 76, and Avril Jones, 58, are accused of her abduction and murder, and of fraudulently claiming £182,000 in benefits by pretending she was still alive.
The couple, who deny all the charges against them, went on trial before Lord Matthews at the High Court in Glasgow yesterday.
It is alleged Cairney and Jones abducted Ms Fleming at her home at Seacroft, Inverkip, locked her in a room, assaulted her, cut her hair and bound her arms and wrists with tape on various occasions between 1 November, 1997 and 5 January, 2000.
The pair are accused of murdering Ms Fleming, who would now be 37, by unknown means at some point between 18 December, 1999 and January 5, 2000.
It is alleged that between 18 December, 1999 and October 2016 they pretended to Department for Work and Pensions officials that Ms Fleming was alive, and claimed state benefits, obtaining £182,000 by fraud.
The pair also face two charges of attempting to defeat the ends of justice.
It is alleged they disposed of, destroyed or concealed the remains and personal effects of Ms Fleming between 18 December, 1999 and 26 October, 2017.
They are also accused of trying to board a train to London at Glasgow Central Station on 25 October, 2017 while carrying £3,500 and the keys to a safe deposit box at a bank in London which contained £27,000.
It is alleged they planned to travel and evade police and prosecutors.
The first witnesses to give evidence in the trial were scene examiners who took photographs of Seacroft cottage.
William Ward, 61, and Petra Sharp, 48, documented the property and surrounding area.
Mr Ward was at the scene on the evening of 1 November, 2016, while Ms Sharp carried out work from 2 November, 2016 until March 2017.
Their photographs, which were shown to the jury, showed a house which was “full of clutter”.
Thomas Ross QC, representing Cairney, asked Ms Sharp whether it was possible to exit the building from the front and rear to get to the nearby road, as well as to the foreshore, and she agreed that it was.
The trial continues today.