While it is only to be expected that the preoccupation of my opponent with his speech for the prosecution should prevent his understanding my defence, the same is not true of yourselves. You should bear in mind that while we, the interested parties, take a biassed view of the case, each naturally thinking that his own version of it is fair, your duty is to consider the facts conscientiously; and so you must give your attention to me as much as you did to himThe addition of this sentence is necessary for a proper understanding of the connection of thought. The γάρ is explanatory of the words ὑμᾶς δὲ χρή in section 1.:

as it is in what is said that the true facts are to be sought. For my part, if I have told any falsehoods, I am content that you should treat the truth which I have spoken as itself a piece of equally dishonest pleading. On the other hand, if my arguments have been honest, but close and subtle, it is not I who used them, but he whose conduct made them necessary, upon whom the displeasure which they have caused should properly fall.