Theresa Riggi, described in court as a paranoid and hysterical woman, might have stabbed her children to death because she believed it was the only way of keeping them safe.

Riggi, who was locked in a custody battle with her husband, loved her sons and daughter 'too much', according to her lawyer Donald Findlay QC.

Eight-year-old twins Austin and Luke and five-year-old Cecilia were found dead at their Edinburgh home on August 4 last year.

Their mother admitted killing them when she appeared at the High Court in Edinburgh on March 7, pleading culpable homicide on the grounds of diminished responsibility. She was originally charged with murder.

Her 'possessive' attitude towards the children had been evident since their birth, the court was told on that day.

She insisted they wore 'locators', controlled by her when they were in public places, and later that they carry mobile phones pre-programmed to call her number.

The situation worsened when she and her husband Pasquale Riggi began divorce proceedings which led to a bitter battle for custody of their children.

Riggi, from California in the US, came to live in the UK 13 years ago with her husband, a Shell employee from Colorado, living for several years in Corton, near Lowestoft, and moving to Aberdeen in February 2007. They later separated.

Mrs Riggi and the children disappeared from their Aberdeen home last July and were traced to an address in Edinburgh.

A judge warned they could be in danger just 24 hours before their death when Riggi failed to appear at a divorce hearing that day.

In court last month, Alex Prentice QC, prosecuting, said that on the evening of August 2, at around 11.30pm, Riggi spoke to her husband on the phone.

Mr Prentice said she accused him of being in collusion with their solicitors and asked if he would take the children away.

On being told that she 'left him no choice', Riggi replied: 'Say goodbye then.' And she hung up.

Two days later building manager Derek Knight found the bodies of the three children after a gas explosion at houses in Slateford Road, Edinburgh, where Riggi was staying in a property rented by a friend.

Riggi was seen rocking back and forth on the second-floor balcony of the property before she 'intentionally' fell head-first, the court was told.

She sustained several injuries, including four to five stab wounds to her body, which were believed to have been self-inflicted, and spent weeks in hospital, making her first court appearances there when part of the infirmary was temporarily designated as a court.

When police entered the house in Slateford Road, they saw the three children lying side by side on the floor. They also found three knives nearby, each covered in blood.

Mr Findlay told the court she was intent on suicide on the day of the killings and had left a space for herself between the children's bodies. He said that, if possible, 'she loved them too much'.

A report into Riggi's mental state identified narcissistic, paranoid and hysterical personality disorders.

The children's father is still struggling to come to terms with their deaths.

He said: 'The loss of my three beautiful children has been an overwhelming tragedy. Nothing can be said at this or any other time which can mitigate what has happened.

'I and my extended family loved Austin, Luke and Cecilia dearly and they will live in our minds and hearts forever.

'I don't know what lies ahead but wherever life takes me, my friends and family, it will be with the memory of a dreadful loss and with gratitude for all the good times spent with Austin, Luke and Cecilia.'