The nine-year-old observed the scene with her 11-year-old brother from the playroom window of their mother's home in Ascot, Berkshire.
She later told police how the pair had heard "banging" as pilot Robert Brown, originally from Edinburgh, bludgeoned 46-year-old Joanna to death.
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Hide AdThe attack - on October 31 last year - took place following lengthy rows over divorce.
Brown admits killing his wife but denies murder and obstructing a coroner from holding an inquest.