About two years ago a nasty little local case popped up where newly minted policeman decided to throw his career away after five months on the job.
The news details are here. The site and the commentary are not pro-police, but it has all the news articles collected in one place.
After a trial this happened
As of today his sentence to one year in jail (and he confessed to the misconduct) was overturned.
I’m not great with reading court case opinions - Court Opinion here (PDF) - (Warning some graphic details). Why exactly was his conviction overturned if the Judge had discretion to convict him? Why did the Judge sentence him in the first place if he was found innocent of the charges?
The charge of misconduct can be for unlawful acts, or acts committed that while lawful, were still wrongful.
You can only be convicted of a crime with which you are charged and the Defendant was charged with the first kind, not the second. The charge of misconduct in office that he was convicted of was based on the fact that he committed the other crimes.
It therefore made no sense to acquit him of the other charges but convict him of the misconduct.
I can’t access the site with the opinion while I’m at work, but it sounds like the OP is mixing up conviction and sentencing. The judge may have had complete discretion as to the sentence to be imposed once the defendant was convicted of misconduct in office, but to convict him the judge still had to find that each of the elements of the crime had been proven beyond a reasonable doubt.