Daniel de Costa’s interview with police the day after he stabbed Devizes man Matthew Baggott to death was described as an “exercise in deceit” at Winchester Crown Court today.

In his closing speech to the jury on the fifth day of the murder trial, prosecution barrister Ian Lawrie told the jury that the interview was extraordinarily detailed and delivered with great clarity of recall.

He said: “This is not the evidence of a man suffering with any great impairment of mind.”

He agreed that evidence had shown that de Costa was impulsive on occasions but added “impulsivity does not preclude calculation or deliberate action.”

Mr Lawrie also described de Costa as being very sly and having a Jekyll and Hyde character, capable of explosive, impusive behaviour but also of deliberate action and pre meditation.

He pointed to the way that de Costa was able to give accurate details of the drugs he had taken on the day of the killing, September 6 2007, and giving a lengthy description of mental conditions such as Asperger’s Syndrome and ADHD (Atttention Deficit Hyperactivity Disorder) from which he claimed to suffer.

But Nigel Pascoe QC, defending, pointed in his closing speech to a wealth of medical evidence supporting that de Costa had suffered from ADHD from the age of two.

Mr Pascoe told the jury: “This was no planned killing nor anything like it but an explosion of violence between two men who not long before had been cuddling.”

He said the jury had to decide what level of responsibility must lie on de Costa’s shoulders adding “If you have a psychopathic disorder you cannot take it off like a back pack whenever you choose.”

De Costa, 31, of Kingsbury Square, Melksham, has pleaded guilty to manslaughter but denies murder on the grounds of diminished responsibility.

The trial continues.