A woman who killed her husband by repeatedly hitting him over the head with a hammer might have been “moderately depressed” at the time, a court has been told.

Sally Challen, 57, of Ashton Place, Claygate, admits to intentionally killing Richard Challen, 61, at their marital home in Ruxley Ridge, Claygate, on August 14, last year, but denies murder on the grounds of diminished responsibility.

At her murder trial at Guildford Crown Court on Monday, the jury heard evidence from Dr Timothy Exworthy, a consultant psychiatrist who interviewed Mrs Challen on three occasions following her arrest last August.

He told the court: “In my opinion, there is evidence Mrs Challen was suffering from a depressive disorder of a moderate severity at the time.”

The court was told Dr Exworthy based his diagnosis on Mrs Challen’s medical records since 1971, emails she had sent around the time of the killing and police interviews, as well as his own interviews with the defendant.

He told the court, according to GP records, Mrs Challen was prescribed antidepressants and was complaining of “domestic stress” brought about by fears her husband was having affairs and using prostitutes.

The jury was told Mr Challen had admitted to the defendant in 2006 that he had visited a brothel in Surbiton called Pandoras and in 2009 the couple had argued after a local news TV channel reported on sex workers at the establishment.

Dr Exworthy said: “Her account was, they were watching telly together and she accused him of helping to run the sex ring on the news article and they had then had a number of arguments.”

Dr Exworthy also told the court Mrs Challen had told him she had visited the defendant’s house in the middle of the night with a hammer in the months leading up to the killing.

He said: “She said she was going to hit him over the head with it. The door to her husbands bedroom was shut and she told me she did not attempt to enter and left the house.”

She also admitted to entering the house in the night on several occasions to look at the text messages on his mobile phone, which he kept in a shoe next to his bed, the court heard.

Dr Exworthy said the defendant had also had thoughts about killing herself in the run up to her killing her husband and had written several suicide notes.

He said: “She said she had thoughts about swerving her car into an oncoming truck.”

However, during cross-examination, prosecutor Caroline Carberry questioned Dr Exworthy on whether Mrs Challen had been moderately depressed at the time of the killing.

She put to the witness that Mrs Challen had continued to work and take part in social engagements in the weeks leading up to Mr Challen’s death.

She said: “According to those around her at the time of the killing she seemed a little brighter and was back to her ‘old self’. Taking into account that evidence, that would point away from a persistent low mood.”

Dr Exworthy agreed with Mrs Carberry that a person with moderate depressions would have difficulty with social activities and working.

The trial continues.