I agree, somewhat with the first statement. But, that assumes a normal distribution of the public become police officers. Anecdotally, I would say that there are a higher percentage of people drawn to law enforcement who crave power and control, than exist in the general population. And, in my experience, people who crave power and control, tend to prioritize keeping power and control over other moral guidelines. Obviously does not apply to every law enforcement officer - just an observation.
As for any given situation - I would not believe a person solely because of their occupation, nor would I automatically disbelieve someone based on their past deeds. Not all criminals are liars, and not all police officers are truth-tellers. I'd be open to allow that either or both could lie, or either or both could be honest, given the various motivations a situation presents.
But, I don't prefer one over the other before I hear what they have to say.