The judge in the case of teacher Mark Parnham, who is accused of murdering his wife, has told the jury to acquit him if they are sure he acted in self-defence

Judge Richard Brown told the jury of seven men and five women at Lewes Crown Court: "You have got to consider whether the force used by him was unreasonable.

"If it was unreasonable, he cannot have been acting in self-defence. But if it was reasonable, he cannot be guilty of any offence."

Parnham is charged with murdering wife Jillian, 38, at their home in Millmead, Ashington, near Storrington, on March 5 last year.

The court has already heard that the couple rowed over Jillian Parnham's affair with work colleague Chris Worth.

All three taught at Millais girls' secondary school in Horsham.

Parnham told the court yesterday that his wife had taunted him and that she hit him first with a metal bar.

He ended up using it to hit her repeatedly on the head - blows which proved fatal.

Today the judge asked the jury to consider whether Parnham had intended to kill his wife.

He said: "You have to ask yourselves if, when the defendant delivered the blows that proved to be fatal, he intended to kill or at least cause her really serious harm."

The judge told jurors if they did not think Parnham had acted in self-defence, they would have to decide whether he had been provoked.

He said: "If the prosecution makes you sure he was not provoked, then he will be guilty of murder.

"If, on the other hand, you conclude he was provoked, the verdict will be not guilty of murder but guilty of manslaughter by reason of provocation.

"It may be Jillian's conduct provoked the defendant and caused the defendant to suddenly and temporarily lose his self-control.

"The reality is, these days many people have affairs, many relationships break up because of affairs.

"If loss of temper at your partner's infidelity might provide a defence to murder, you might think the law was totally out of touch and you might think the law had lost its way."

The judge said the jury were entitled to take into account the events leading up to Jillian's death and the lies Parnham had told immediately after.

The jury was sent out at lunchtime and was due to begin its deliberations this afternoon.