How did Evans manage to get blood in the cell?
McLeery was the close friend of Evans. He had come for invigilating Evans. He had a rubber ring for getting rest against piles. The ring was semi-inflated. It had a pig's blood that was kept by the person in his suitcase. It has some chemicals and some real blood to prevent it from clotting. It was filled in the rubber-ring so it was looking semi-inflated.