//After a Not Guilty verdict, he or she must remain innocent…//
As I said, Corby, you are getting legal terminology and convention confused with fact.
If I walk into Sainsbury’s, put a packet of crisps under my coat and walk out without paying, then eat them on the way home, a crime has been committed by me. I have committed theft; I have taken the packet of crisps from Sainsbury’s without their consent and with intent to permanently deprive them of it. They are a packet of crisps short and I am one to the good.
If nobody saw me commit this unspeakable act and I was not caught on CCTV, there would be no evidence to support a criminal prosecution. I would not be prosecuted; I would not be found guilty. But I committed the crime nonetheless and I am guilty of it. But by legal convention I am, and will remain “innocent” (or more properly, “not guilty”, because we’re talking of legal convention, not fact). And quite right so.
//…and therefore, there has been no offence committed.//
If you contend that no offence has been committed unless and until somebody has been convicted of it, then the police would have no “unsolved crimes” on their books. But clearly they do – lots of them. You could argue that they remain merely "allegations" but, in the case of Sainsbury's and their packet of crisps, there would be no doubt in my mind, having been the person who stole them, that a criminal offence had been committed.