A depressed woman who tried to kill her teenage son by firing an air gun at his head has been jailed indefinitely for public protection.

Jane Pentney will have to serve a minimum of three years before the parole board considers whether it is safe to release her.

A judge said the 43-year-old, of Lavender Hill, Tonbridge, was "extremely intoxicated" when she decided to kill her two sons and then herself on January 4.

The injuries, he said, were mercifully "not so great".

There had been other serious attacks on the boy, now 16, in 1988 when she attempted to smother him after taking an overdose of drugs. She lost her temper and "beat his face to a pulp".

Judge James O’Mahony said of the previous violence: "Social Services will go to any lengths not to interfere some times, when the indications are they should."

Tracey Ayling, QC, defending, said: "The whole family has been affected by the consequences of her actions in January. She and her husband have now parted."

Jordan and his brother, aged 14, found themselves without a mother because of her imprisonment. They would be "inaccessible" to her for some time.

"What led her to take a rifle to her son’s head that night remains a mystery," said Miss Ayling. "A wish to kill her children has always been followed by a wish to kill herself."

Judge O’Mahony said it was a difficult sentencing exercise. Pentney had suffered from depression for years - but there was no question of a disposal under the Mental Health Act.

The judge added that almost a year spent on remand would count towards the sentence.