Antoine Denis, 66, was found slumped on his back in the bedroom of his flat in Chatham, Kent, in January this year.
Detectives at the scene pronounced father-of-four Antoine dead but found nothing that suggested a crime had been committed.
It was only when undertakers arrived to remove the body that they found blood and a 12CM (4.7in) knife stuck up to its hilt in Antoine’s back.
One of the officers received a verbal warning following an internal police investigation into the handling of the as yet unsolved murder.
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