Umbridges Motives (some spoilers)

[Dave]

No: HPFGUIDX 89351

After reading Order Of The Phoenix, (at least twice), I cannot 
understand why, a senior ministry employee, like Umbride, would 
resort to sending the Dementors to 'Kiss' Harry. I know the reason 
she gives, in chapters 32 and 33, (paraphrasing) that she wanted to 
help her boss, the Minister of Magic, but would there not be 
reprecusions for such action.  The equivilent of the death penalty 
for being awkward and inconvienient sent on a teenage boy, Harry 
Potter, without a trial etc. 
Is there something else I'm missing?
Dave