diction: declare vs. announce?

[maoyueh]

Please take a look at the following two sentences:

a. The judge declared the accused innocent.
b. The judge announced that the accused was innocent.

I know a is correct, but I doubt whether b is also acceptable. What are the nuances of these two verbs? b sound unnatural to me, but I am not sure. I need language experts's opinions. Thank you very much.

[Grumpy]

Both mean very much the same, ie making something publicly known, but "declared" has more of a solemn connotation to it, which is more appropriate in this legal context. In fact, I think there there is actually a specific legal device called a "solemn declaration".
I can visualise "announcing" the results of a beauty contest, but not "declaring" them