Prosecutors had alleged Linda Wise, 47, shook Isaac Rowlinson when he was just 13-weeks-old and caused him brain damage.

Isaac, the son of Lancashire Police detectives Lisa and Paul Rowlinson, died 10 months later after suffering an epileptic fit.

Wise, of Gaerwen, Anglesey, north Wales, had denied manslaughter at Liverpool Crown Court.

Mr Justice David Clarke had informed the defence and prosecution on Thursday, in the absence of the jury, that he considered there was insufficient evidence against the defendant.

On hearing that announcement both Miss Wise and Isaac's mother burst into tears.

The judge brought the seven women and five men of the jury into the court and told them he had been "greatly troubled" by the prosecution evidence since around halfway through the case.

Among other reasons, he said, in his view the jury could not reasonably conclude that the bleeding on Isaac's brain took place in the timeframe prosecutors alleged.

He added: "The loss to the parents of Isaac is incalculable and the defendant herself has been under a cloud of suspicion for a long time. And that cloud may not lift at once now the case has come to an end."

Miss Wise, who has worked for the actor Ed Stoppard, Greek shipping magnate Philippe Niarchos and a number of minor European royals, closed her eyes as the jury foreman gave the not guilty verdict.