The former girlfriend of a man accused of murder told a court she could not remember giving evidence in two previous murder trials because of "brain fog".

Alexandra Tierney, 47, was giving evidence for a second day at the trial of Ronnie Coulter, 48, from Wishaw, North Lanarkshire, who denies murdering Surjit Singh Chhokar by stabbing him in Garrion Street, Overtown, on November 4, 1998.

The jury has heard Ms Tierney, known as Sandra, gave evidence at the trial of Ronnie Coulter for murder in 1999 and at the murder trial of his nephew Andrew Coulter and David Montgomery in 2000.

All three men were acquitted of the murder of Mr Chhokar at the trials.

She was asked by prosecutor Alex Prentice QC: "Do you remember giving evidence in the trial of Ronnie Coulter?" She replied: "No."

The prosecutor then asked: "You have no memory of giving evidence in the trial of Andrew Coulter and David Montgomery?" Ms Tierney responded: "No."

She was asked why she had no memory of this and she said: "I just can't remember. I've done my hardest to black it out."

She then told the jury she had "brain fog" caused by illnesses and medication she takes.

Ms Tierney said she suffers from Dercum's disease and was asked how that affects her memory.

She replied: "It can cause brain fog. There are no consultants in Britain. The only consultant you can see is in the US."

Ms Tierney was asked by Mr Prentice how she knew this illness affected memory and said: "I learned from a website because there's not a doctor in the UK that deals with it."

She was read a transcript from the previous trial and agreed that she was telling the truth then.

Ms Tierney told those trials Ronnie Coulter asked her to dispose of a black bag of wet clothes and a box containing knives the day after Mr Chhokar died.

Ronnie Coulter has lodged a special defence to the murder charge blaming his nephew Andrew Coulter and David Montgomery.

Both men in evidence denied having anything to do with the killing of Mr Chhokar.

Ronnie Coulter denies all the charges against him. The trial before judge Lord Matthews continues.