Are you reading the same story? This portion says they are investiagating some of the officers for not doing their job
"A number of police officers are facing an internal disciplinary investigation over the handling of the case after it emerged that Miss Mahmod had told police four times that she feared for her life". "
And if the investigation shows that mistakes were made, I hope that the appropriate punishments are meted out. An investigation is standard procedure in such a situation and is not a declaration of guilt.
A legally sane and law-abiding person has the last word in matters such as this.
It’s probably standard operating procedure to ‘launch an investigation’ if there is a media outcry about the story. But it sounds like the police did all that they could legally do. Of course, that won’t stop some in the media from screaming about them.