Carl Wayne Bowen admits stabbing Jamie Yeates but denies his murder
A 42-year-old man accused of murdering his stepson was "jealous, possessive and controlling" but not mentally ill, a psychiatrist has told a jury.
Carl Wayne Bowen admits killing Jamie Yeates, 15, but denies murder on the grounds of diminished responsibility.
Dr Philip Joseph told Swansea Crown Court it was more likely Mr Bowen lost control, and did not become psychotic.
Mr Bowen, from Llanelli, also denies the attempted murder of Jamie's sister Kimberley and their mother Maria.
Jamie, a promising jockey, was stabbed to death at the family home in Llanelli on 8 January.
It is alleged Mr Bowen burst in on Jamie as he slept and stabbed him 18 times with a kitchen knife.
The blows severed his spine and several ribs, the court has been told.
Dr Joseph told the court the defence seemed to be suggesting that Mr Bowen suddenly became psychotic, killed Jamie, and then came back out of the pyschotic state.
He said he had worked at Broadmoor high security hospital and that no-one there suffered from "five-second psychosis".
"Where has it gone?" he asked. "He had never had one [a psychotic episode] before and never had one since."
The defence has argued that Mr Bowen's jealousy of his wife Maria, coupled with the amount of alcohol he had drunk early on 8 January, "tipped him over" into a mental illness.
Dr Joseph said it was more likely Bowen felt he was losing control.
Shortly before the killing both Maria and his step daughter Kimberley had said they were leaving the house and Jamie had begun visiting his grandparents without his permission.
Peter Rouch QC, defending, has told the jury that Mr Bowen did not deny stabbing Jamie 18 times, but argued that he was suffering from diminished responsibility at the time because of an abnormality of mind.
The jury has now heard all the evidence in the case and will hear closing speeches by Elwen Evans QC, for the prosecution, and Mr Rouch on Thursday.