Crime Correspondent Stephen Cape: The verdict was probably a surprise for Sullivan

Six-month-old Caroline Jongen died of brain damage last April, five days after Sullivan, 27, shook her violently at the family home in north London.

Sullivan pleaded guilty two weeks ago to involuntary manslaughter.

Police had expected Sullivan to be jailed for five years, but Judge Mr Justice Mitchell decided she needed help, not prison.

Judge Mitchell, passing sentence at the Old Bailey in London, said there were "exceptional circumstances" regarding Sullivan's mental health for not sending her to jail.

Sullivan was alone with the baby at the Jongens' home

The court was told earlier that Sullivan has an IQ of 81 - well below the average of 100 - and should not have been allowed to look after Caroline.

The delayed development was made worse by a thyroid deficiency.

The judge said it was tragic that her lack of mental capabilities had not been detected earlier.

He said: "You were unable to think flexibly or adjust your mind to the developing circumstances - particularly in emergencies or what you perceived were emergencies."

Crime Correspondent Stephen Cape: Sullivan could have had a nervous breakdown in prison

He added that despite her training, she did not have the capacity to exercise reliable judgement.

Sullivan will now be able to return to Australia for psychiatric and psychological treatment.

Muriel Jongen: No comment

Caroline's parents, City fund manager Marcel Jongen, 41, and financial analyst Muriel, 36, comforted each other in court as Judge Mitchell added: "Nothing can put the clock back or restore that baby to her mother and father, or end the pain of the parents or their anguish.

"I can only hope - having braved this hearing - they will understand I have decided to allow her to return to Australia."

After the hearing, the couple left the court without making any comment.

Later, solicitor Karen Todner, acting for the Sullivan family, said: "Louise is extremely distressed. She will be returning to Australia as soon as possible."

Sullivan 'loved child'

Miss Todner also read out a statement by the family which said: "Louise Sullivan bitterly regrets that her actions led to Caroline's death.

"We are pleased that the judge was able to show compassion to a girl who has never deliberately sought to harm a child which she cared for and loved."

The statement gave Sullivan's version of events on 17 April last year when the baby suffered injuries that led to her death.

'Shake and shout'

It said: "During the course of the morning Louise believed that Caroline suffered a fit or convulsion. Louise had never experienced such a situation before.

"During the course of her training in Australia Louise was taught the 'shake and shout' method.

"Most regrettably it was this course of action which ultimately resulted in Caroline's death.

"This is not a case which is about temper or loss of patience.

"This is a case of a girl who panicked and made a mistake with tragic consequences."

'Never shake a baby'

After the case, Detective Inspector Philip Wheeler warned about shaken baby syndrome - a potentially fatal form of child abuse that rose to prominence during the trial of Louise Woodward, the au pair who was found guilty of shaking baby Matthew Eappen to death.

He said: "We have to educate people about the consequences, so I would say, never, ever shake a baby."

Sullivan, wearing a blue suit and with her blonde hair tied back in a clip, left the Old Bailey with her grim-faced parents Barry and Louise.