It is interesting that here the 3 of the top 4 "serial killers" are in fact women. (Amelia Dyer, Amelia Sach & Annie Walters) All three were supposedly carers of children and are believed to have killed 100s between them the forth a Doctor who murdered old women and men. Most recently a nurse has been convicted of murdering children in her care. In terms of numbers "Jack the Ripper" was a novice and our other notorious serial killers are Rose and Fred West and Myra Hindley and Ian Brady. While Mary Ann Cotton killed at least 21 people (three her husbands) making her a top scorer.