Expert reports, however eminent the expert, are just opinion. Did the report actually say that the marks to Sheila's neck definately could not have been made with a gun with a silencer? Or did it say that in his opinion the marks were consistent with having been made by a gun without a silencer? In the absence of any viable challenge to the blood evidence the CCRC will have just weighed up the opinion against the forensic evidence and the rest, as they say, is history.