There would have to be if all the incriminating evidence was fabricated.
I have given my opinion. The relatives dripped poison in the ears of EP. That is not an offence. DCI Jones rightfully shut them down but unfortunately the relatives were still able to exert undue influence. Particularly RB with senior officers. There did not appear to be any proper management controls and oversight in place. DS Jones was pretty much allowed to run the show. He was there at every turn. A relatively junior officer who had no experience of a mass shooting.
He alone fabricated the outside of the silencer and put the frighteners on JM to secure her testimony.
The lab did the rest for which there is overwhelming evidence.
The above is not an 'industrial frame'. It is very similar to the case of Stefan Kiszko:
Kiszko BamberLay Witness 4 x teenage girls lied for a laugh Mugford
Police Officer Holland charged with perverting DS Jones
course of justice
Forensics Outteridge charged with Outteridge transferred to Huntingdon
perverting course of justice when Bamber exhibits under
examination
https://en.wikipedia.org/wiki/Murder_of_Lesley_Molseed