Forensic Psychiatrist Professor Nigel Eastman has been giving evidence for the defence at the trial of Chinese businessman Anxiang Du who is accused of murdering four members of the Ding family in April 2011.
In an earlier interview with the Forensic Psychiatrist, Anxiang Du told Professor Eastman he had purchased the knife several months before the killings to take his own life. During a period of depression over the long running legal dispute with the Dings, he said, he wanted to "leave this world."
On the day of the stabbings Mr Du said he had remembered the knife, which had been kept in a bag and took it with him as he travelled from Birmingham to Northampton. He said, he had the intention of using it to force the Dings to pay him the money, he felt was owed to him following a long running legal dispute.
Asked if he planned to harm them, he replied: "Possibly, I had that thought."
He claims he did not have the forethought to contemplate killing them and if he had he would not have gone to their home. He also said if the Dings had apologised to him he would not have carried out the attack.
On arriving in Wootton he walked through their open garage door and into the garden where he saw Jeff Ding in the kitchen. After walking inside, Mr Du asked Mr Ding for money, but was told he was stupid and a fool. He was told to leave the house or the police would be called.
Anxiang Du says then without saying anything, he pulled the knife from his bag. He says, everything went dark and Jeff Ding's image and voice appeared "distorted, hard and ugly" as he carried our his attack. Professor Eastman described this as evidence of a heightened state of arousal.
Mr Du said he then felt a hand tugging at his arm which was that of Helen Ding and turned the knife on her. He stabbed both but can not remember how many times. He then said he'd heard a noise upstairs and after going up to investigate found the Ding's daughters Xing and Alice. He stabbed them both, though again he could not recall how many times.
Professor Eastman says as Mr Du recounted the killing of the children he said he did not know why he had done it and had sobbed uncontrollably, describing it as a "big sin."
Mr Du says he then fell asleep and woke when it was dark. He saw a wallet and car keys nearby and decided to make his escape. Though, initially he told Professor Eastman he had thoughts of going to see the Ding's business partner Paul Delaney, and "harming him in the same way."
However, after being unable to find his way to Mr Delaney's house he made his getaway - driving from Northampton to the M40.The case continues this afternoon at Northampton Crown Court.