guardian kay-ann morris is on trial for murdering her niece shanay , 7 .
paramedics found shanay lying cold and stiff in bed at nottingham home .
morris and mother , juanila smikle , claim she had fallen down the stairs .
paramedics later found 50 bruises on girl 's face , torso , arms and legs .
prosecution say death was due to ` sustained , vicious and brutal beating '