A misconduct hearing found the mistakes of Det Con Philip Payton, of Humberside Police, caused investigations to stall.
It follows an Independent Office for Police Conduct (IOPC) inquiry into six cases he led between 2015 and 2017.
All the cases involved vulnerable victims and gross misconduct had been proven, the IOPC said.
Miranda Biddle, IOPC regional director, said: “DC Payton’s handling of these investigations fell so far below the standards of what members of the public are entitled to expect and his failures have had a devastating impact on the families involved.
“Had it not been for the actions of his colleagues in identifying and rectifying this litany of mistakes, his incompetence might have resulted in serious crimes going unpunished.
“He has at no point taken responsibility for his extremely poor performance and this kind of response severely erodes trust and confidence in the police and anyone who behaves in such a way can have no place in policing.”
IOPC findings on Det Con Philip Payton
* Provided dishonest updates to families and colleagues, missed key evidence and incorrectly logged crimes while investigating sexual assault and rape allegations
* Perpetrators were only prosecuted after a different detective was appointed to take charge
* Arranged for a suspected rapist’s home to be searched, only to authorise the return of property despite being aware of an electronic device appearing to contain traces of indecent images of children
* Failed to process and manage case material or submit files to the Crown Prosecution Service in a sexual abuse investigation
* His statement said he felt “unsupported and overworked”, but the IOPC found he was applying for additional responsibilities at the time
The police watchdog said Mr Payton left his role earlier in March, but would have been dismissed without notice had he not already resigned.
At the two-day misconduct hearing, which concluded on Tuesday, Mr Payton was found to have breached the police standards of professional behaviour relating to duties and responsibilities, authority, respect and courtesy and honesty and integrity.
The IOPC said it had been assured that Humberside Police had undertaken an internal review and “implemented additional supervision approaches to ensure that concerns are flagged and addressed to prevent such failures reoccurring.
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