On 3 November 1828 a warrant was issued for the detention of Burke, Hare and their wives; Broggan was released without further action.[84][85] The four suspects were kept apart and statements taken; these conflicted with the initial answers given on the day of their arrests.[84] After Dr Alexander Black, a police surgeon, examined Docherty's body, two forensic specialists were appointed, Robert Christison and William Newbigging;[86][lower-alpha 12] they reported that it was probable the victim had been murdered by suffocation, but this could not be medically proven.[89] On the basis of the report from the two doctors, the Burkes and Hares were charged with murder.[90] As part of his investigation Christison interviewed Knox, who asserted that Burke and Hare had watched poor lodging houses in Edinburgh and purchased bodies before anyone claimed them for burial. Christison thought Knox was "deficient in principle and heart", but did not think he had broken the law.[91]