Or perhaps the reason that we don't see corruption in this case is because none exists. There is also no reason for the police to have done anything corrupt - I think I've lost count now of how many times I've asked why they would need to lie or falsify evidence and not received an answer.
There are also those who appear to have an aversion to the concept of Jeremy's guilt, and hide behind the police corruption claim every time their argument stalls... just sayin' 
I personaly feel that it's flawed reasoning to suggest the police had no reason to be corrupt. How likely is it that a case would remain notoriously controversial for 27+ years, soley due to the machinations of somebody in prison, who couldn't even work out from the very beginning that if he told his girlfriend, there might be a chance he would end up in prison in the first place?
I also think it's disingenuous of you to suggest that you've never received an answer. You've received many answers about why police would need to use corrptive practices but on each occasion, you've chosen to write them off. The entire forum is based around this, so it's not possible for it not to have come up in forum conversation.
my own view is that he police are not going to deliberately provide evidence of a bungled raid / fabricated case, alongside their official case. I've already posted about how absurd I feel it is for people to actually consider that the police would kindly evidence their own corruptive practices, in a uniform manner similar to the actual prosecution case, to enable researchers many years later, to satisfy demands that people 'prove' corruption. It's like suggesting that a Bank which is cooking the books, retains a second record of it's actual (corrupt) accounts and publishes them, alongside the falsified set, just to help anyone who wants to reference that banks' corruptive practices having taken place.
There are many anomalies regarding date and location of silencer, i.e. custody in two places at once (just one example). No offence but people like you will always continually reject such evidence and sneer at it and scoff at. So what's the point in even debating?