A man accused of murdering the mother of his children will not give evidence at his trial.
Torbjorn Kettlewell intends to use the defence of diminished responsibility which would make him guilty of the lesser offence of manslaughter, a jury was told.
Kettlewell stabbed Kelly Franklin, 29, more than 30 times after confronting her in the street in Hartlepool.
The couple had recently split up, and Kettlewell was annoyed that Ms Franklin did not want to speak to him or give him details of the care of their three children.
Mr Justice Jacobs told the jury at Teesside Crown Court there are four conditions they must be satisfied are met if they are to accept a diminished responsibility defence.
"You have to find that when he killed Ms Franklin he had an abnormality of mental function," said the judge.
"You have to find he was suffering from a recognised mental condition.
"That condition substantially impaired his ability to make rational judgments or control his behaviour.
"The abnormality of mental function caused him to kill Ms Franklin."
The jury was told it was up to Kettlewell's defence team to prove he met the conditions.
Dr Mark Turner, a consultant psychiatrist, told the court he had examined Kettlewell and studied his medical records.
"I found he was fit to plead and take part in his trial," said Dr Turner.
"I found he had an abnormality of mental function, and I found it was a recognised mental condition, borderline personality trait linked to a mild depressive episode.
"This had some impact on his ability to control his behaviour, but that impact was not substantial.
"I found that his condition did not have a substantial impact on the commission of the offence."
Dr Turner said in his opinion Kettlewell does not have the defence of diminished responsibility available to him because he fails two parts of the four part test.
Under questioning from Richard Wright QC, for Kettlewell, Dr Turner said it was for the jury to decide if the conditions are met.
Jamie Hill QC, prosecuting, told the jury a report by another psychiatrist, Dr Pratish Thakkar, also found Kettlewell did not qualify for a diminished responsibility defence.
Kettlewell, 30, of Oval Grange, Hartlepool, denies murder on August 3.
Julie Wass, 48, of Kipling Road, Hartlepool, also denies murder.
She admits assisting an offender.
The case continues.