In everyday life we must, and try to, say what we mean. This is doubly the case in giving evidence. Look at this:
QUESTION; You didn’t call out for help?
REPLY: No.
By this reply, the witness has now sworn that he/she DID call out for help. We see this if we express the intended reply at length –
“Yes, I did not call out for help” (or, “I did not call out for help”).
Counsel must be careful of this. A question and its reply will enter the transcript (where there is one). That transcript is the only admissible record of the trial, in any appeal. It is not (practically) open to correction. Only the witness can correct his or her mistake, if there be one, because what is in issue is what is meant and only the witness may explain that. There are no witnesses in an appeal hearing, to do that explaining.
What Counsel is presumably intending is to elicit the reply “I did not call out for help”, OR, “I did call out for help”.
Alternatively, the proceedings have arrived at an intended (or otherwise) crisis point. Perhaps the Counsel is dozy and complacent and the witness is not, or it is the reverse, (or they both are). Perhaps the significance of calling for help, or not calling for help, is considerable. Perhaps not calling for help is not credible. That implies the witness is not credible.
Better still, perhaps the witness is challenging the Counsel and means to convey – “So what, if I did not call out for help?” This is unlikely. A witness of that calibre would not make the grammatical mistake of simply saying “No” in reply to the question. The reply from such a person would be – “That’s right, I did not call out for help.”
The modern age (possibly prior ages also) has trouble with negation in English speech but there is little excuse for it. The English rule is clear; a double negative is an affirmative.
“I can’t get no satisfaction” means “I can get satisfaction”. In fact, it implies that it is next to impossible for the speaker to fail to get satisfaction. From the little we know of Mick Jagger, that was true, but we feel he would have replied “No” to our question; he is, or was, that type of person also.