Mairead Philpott tells prosecutor Richard Latham QC that it is "possible" her husband Mick got out of bed to light the fire.
She agrees with him that there was no mention of this in her defence case statement.
Mr Latham asks why she would say nothing of this in her interview if she was innocent. Mairead says she was following advice.
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At least one person has died and 18 homes have been destroyed as wildfires rage through southern California.
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