Here is the relevant part of 'Annie' Eaton's, 72 page witness statement that she made to the COLP investigators, regarding Sheila's bloodstained knickers, and how she could tell the difference between ordinary blood, and menstrual blood:-
please note, the advice DSS 'Mick' Ainsley gave her to make sure she told the court about the different smells of ordinary blood, as opposed to menstrual bloodDCS