I'm not surprised that the chief constable is trying to keep the lid on the biggest stitch up in the history of the A and S force.
Chris Jefferies was arrested on suspicion of murder without a shred of evidence and there were leaks by his force to the media which enabled and gave them the green light to assassinate his character with the most lurid reports that they could dredge up.
The intent of the police at that time was to embark on a stitch up of Jefferies who was known to be alone in his flat, had the opportunity, had a car and had a key to Joanna's flat. The police had hit a brick wall in the investigation and the media vilification was going to deny him an unprejudiced jury. His dna would be in the flat because he owned the place and he would have been an easy target to frame.