Danny O'Brien: Bound and gagged

She later walked into a police station and told detectives she had hit Mr O'Brien with the axe after he had threatened to kill both her and Amy.

Prof Kopelman, consultant neuro-psychiatrist at St Thomas's Hospital, said amnesia in homicides was most common in what he called "crimes of passion".

He said he had interviewed Ms Charlton about her claims she did not remember the killing until the memory came back more than a month after the incident.

He told the jury: "All I, as an expert, want to tell you is that this kind of amnesia can occur.

Child witness

"It is plausible and there have been related similar cases in the past."

Mr O'Brien was found with an axe embedded in his head on 23 May last year.

The court has heard how he was wearing a gag, a blindfold and handcuffs and had been hit at least 20 times with the weapon.

The case continues.