Police officers have told a court of the "astonishing calm and coldness" displayed by a mother, formerly of Lichfield, who had just the night before killed her young son and daughter in a Spanish hotel.

Lianne Smith, 45, has admitted smothering five-year-old Rebecca and 11-month-old Daniel with a plastic bag at the Miramar Hotel in Lloret de Mar on the Costa Brava in May 2010.

She is on trial at the Provincial Court in Girona, north-east Spain, so a jury can determine whether she is criminally responsible for the children's deaths.

Her defence is seeking an acquittal, claiming she was in a state of "psychiatric disturbance" and suffering insurmountable fear when the tragedy happened. If found guilty, she faces a total of 38 years in prison.

The police officers, who were identified to the court by their badge numbers as is customary in Spain, all agreed that Smith seemed calm when she confessed to the killings the day after carrying them out.

Agent 2681 from the Mossos d'Esquadra, the Catalan regional police force, was among the first officers to get there.

"I was shocked by her attitude, the astonishing calmness and coldness she displayed," he said.

The killings took place shortly after Smith's partner, Martin Smith, was arrested in Barcelona by Spanish police acting on a European arrest warrant.

The family had been living in Spain since 2007 after fleeing Lichfield because Smith's eldest daughter by her first husband had accused Mr Smith of sexually abusing her. The couple also lived together in Cumbria, where Lianne worked as a manager at Cumbria County Council's children's services department.

The trial was adjourned until Wednesday.