Another point of note comes at 17c, where Socrates claims that his speech will be entirely improvised. The speech we are reading, however, does not come from Socrates' improvised speech but from Plato's well-trained writing. Obviously, this is not a word-for-word transcription of Socrates' speech, but is rather a reconstruction by Plato. We find Plato inserting a further layer of irony here, as the words that we are reading are very clearly not improvised.
The concept of irony in Socrates and Plato can be (and has elsewhere been) discussed extensively. Such a slippery concept is difficult to present concisely. That being said, one (but by no means the only) way to consider the significance of all this irony is to point out the essential flexibility of words and language--how the same words can be manipulated to serve different purposes. The end result might be to persuade the jury (and the reader) to mistrust the rhetorical flourishes of both Socrates and his accusers and to pay attention rather to the justness of their claims. Socrates is firmly convinced that his accusers have slandered him and that careful attention to the facts of the case will make this clear. Thus, in his introductory speech, Socrates hopes to do away with rhetoric and sophistry and to focus the jury's attention instead on the facts.