She was caught DUI & driving recklessly last fall, for which she was given probation (36 months if memory serves), ordered to pay a fine, ordered to participate in alcohol education, and had her license suspended. THAT was her first offense, and she was not thrown in jail for that. Essentially the judge gave her a break and said "we'll cut you some slack and not throw you in jail this time -- but if you screw up and violate the terms of your probation, you're going to jail." That is very common for DUIs. She then proceeded to violate the terms of her probation, twice, while making smart-a** comments to one of the police officers. So seems more than appropriate to give her a taste of prison. She clearly wasn't learning from all of her warnings.
In many other courts, judges will make sure you spend time in jail for a first DUI, even if you get probation. DUI is serious and kills innocent people every day. I, for one, commend the judge's resolve.
FYI the court document you cite is from last fall and predated Hilton's later transgressions. So naturally it did not list prior offenses. Take a look at the recent court documents and I imagine they will reference her prior.
Do you have any evidence to support your claim that the judge was unethical and violated the judicial code of conduct? That's a pretty serious charge, and I haven't seen any indication of its truth, other than your comments and the comments of Ann Coulter.