Using a journalist as the central character in a crime novel (or, more accurately, a narrative driven by crime) is that they can get too close to the action.
Dryden recognised he had arrived at the dividing line between being a reporter and a detective. He was reluctant to cross it due to a combination of iinate cowardice and the lack of a blue uniform covered in comforting buttons and insignia (The Water Clock, Jim Kelly)
And here's DCI Pink to Constance Amory in Exit:
"This is not a story; it's a crime. And you aren't a detective, you are a reporter."
Later, in The Water Clock:
(DCI) Stubbs turned on him. "You've got no right shadowing a police office investigation like this. Or for that matter, witholding vital evidence."
Similar to Kurt Wallander in Firewall:
"You and your newspaper are not the ones in charge of this investigation. We are. If you wish to draw your own judgment, we can't stop you. But the truth is going to turn out quite different. Not that you and your editor will give it much space."