A 300-pound(136kg) American woman has admitted to suffocating her boyfriend to death by sitting on him.

Windi Thomas, 44, pleaded guilty to the third-degree murder of Keeno Butler, also 44, on Monday in America, and is set to be jailed for 18 to 36 years.

Thomas repeatedly hit her boyfriend on the head with the leg of a table, after stabbing him.

Her lawyers insisted the killing was unintentional and claiming that Thomas only killed Butler – who weighed 120 pounds – after collapsing on top of him while drunk, but prosecutors said she had also beaten and stabbed him.

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After Butler’s death, an autopsy ruled he had died of ‘respiratory insufficiency secondary to blunt force trauma to the neck and thoracic compression, exacerbated by blunt force trauma to the head'.

Police officers at the scene found a table leg covered with blood.

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