In that link is the report conclusion which says they could if they made a good case for it but they would need to seek a warrant. In this case I think they should push for it to tried to identify the man but do they have other unknown DNA? I think the dead man needs a legal advocate in this case to push for it.

Clearly a crime has been committed taking into account the method of Burial.

"The cases for which a genetic genealogy approach may be considered must be clearly defined to enable an ethical and reasoned decision to be made. Permission from the Forensic Information Database Strategy Board should be required."