I still maintain that if Sheila had been in the kitchen during the fight some grains would have been found. You would be amazed at how long small particles can adhere to feet and what crevices they can get into. The photos are not the feet of a woman who has moved about in a wrecked kitchen in my opinion. One of the best ways to incapacitate a barefoot assailant is to stamp on a foot and there is no evidence at all of this happening.
On second thoughts, you could be right about the sugar. The COA said -
49.
DC Hammersley, the Scenes of Crimes Officer placed plastic bags over Sheila Caffell's hands and feet before her body was removed from the farmhouse.
He saw some blood staining to the back of the right hand, but apart from that the hands, to his eye were clean and the nails intact. The deceased's feet were also free from blood staining and from any debris such as sugar.
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The COA would not say this unless there would have been a good chance of sugar being on a 'dead' Sheila's feet.