burke and hare had removed the body from the house before the police arrived. however, under questioning, burke claimed that docherty had left at 7:00 a.m., while mcdougal claimed that she had left in the evening. the police arrested them. an anonymous tip-off led them to knox's classroom where they found docherty's body, which james gray identified. william and margaret hare were arrested soon there after. the murder spree had lasted twelve months.