A 21-year-old Irvinestown woman wept in court on Friday as a judge jailed her for three years after she stabbed her step-father during a drunken St. Valentine's Day argument.

Omagh Crown Court judge Mr Justice Hart, sitting in Belfast, told Diana Louise Beckett that while he did not believe she was to blame for the initial argument which 'plainly created a volatile atmosphere,' he added that 'nevertheless, the defendant's action in picking up the knife and pointing the knife in the direction of the deceased in such a highly charged and volatile situation in a very confined space was fraught with danger'.

Mr Justice Hart continued: 'By her plea to manslaughter she has accepted that she was not acting in self-defence, nor in defence of anyone else when the fatal blow was inflicted, whatever may have been the reason for her actions earlier that night'.

Beckett was originally charged with the murder of her 39-year-old step-father Stephen Robinson at the family home in Cullaghmore Road, Irvinestown in the early hours of February 15 two years ago after a St Valentine's Day meal went wrong.

Mr Robinson died after having a knife plunged 12 to 14cms into his chest, which sliced his aorta, the main blood vessel coming from the heart.

Prosecuting QC Philip Mateer told a previous court the Crown had accepted Beckett's plea to manslaughter because there was 'insufficient evidence available in order to establish that there was a necessary intent on her part to kill the deceased or to cause him really serious harm'.

At the sentencing on Friday, Mr Justice Hart said given the evidence concerning the number of 999 calls made from the house in the early hours and the evidence of marks and abrasions on both Beckett and her mother Dorothy, he was approaching the case on the basis there had been a 'continuing argument' between all three.

'It is agreed,' said the judge, 'that there was a prolonged and vigorous verbal and physical altercation between the deceased, her mother and the defendant, sparked off by something said by Mrs Beckett to the defendant when Mrs Beckett and Robinson returned home, and the altercation was inflamed by the amount of drink consumed by all concerned.'

During the melee both Beckett and her mother were put out of the house but eventually allowed back in by Mr Robinson and it was then that the trio ended up in the small utility room where the fight continued and Beckett got the knife.

Mr Justice Hart said when she had the knife, Mrs Beckett and Mr Robinson 'grappled' with her in an effort to disarm her.

He told the court: 'During that grappling the defendant wilfully, that is deliberately, inflicted the stab wound that lead to the death of the deceased.'

The judge added that although the prosecution accepted there was insufficient evidence to prove either an intention to kill or cause serious harm to Mr Robinson, he added 'however to take up a knife and point it at someone in such a highly charged atmosphere is itself a dangerous act, and when death results the person using the knife is guilty of manslaughter'.

Mr Justice Hart said the offence itself was aggravated by the fact Beckett had used a weapon and by her criminal record which contains convictions for assault, disorderly behaviour and shoplifting including two thefts which she committed while out on bail.

However, he added that in mitigation there was her guilty plea, her genuine remorse and also that she had lead a 'chaotic life and troubled adolescence'.

In imposing the three year term, after Beckett agreed to spend a further two years on probation, he warned her that if she breached any of her probation conditions 'you will go back to prison'.