Det Supt Andy Brennan led the probe after mother-of-three PC Beshenivsky was killed at point blank range when responding to the armed robbery of a travel agency in Bradford in November 2005.
Faisal Razzaq served just 11 years of a life sentence for manslaughter for his role in the murder of PC Sharon Beshenivsky before he was released from jail in 2017.
Faisal Razzaq is one of three gang members of the original six convicted – including his older brother Hassan and Raza Ul-Haq Aslam, who have also already been released from jail.