I need to give you some general directions as to what you can make of all of this. You cannot speculate about what any of these witnesses would have said, but where a party without explanation fails to call a witness that you might reasonably have expected them to call, if that witness' evidence had have been favourable to them, then although you cannot speculate as to what you think that witness might have said, nevertheless it is open to you to draw a couple of inferences.
The first inference you might draw is that person's evidence would not have helped the party's case. If you draw that inference you can take it into account against the party in question who did not call the witness who you expected might have called the witness, first in deciding whether to accept any particular evidence which has in fact been given either for or against the party and which relates to a matter in respect of which the person not called as a witness could have spoken, and secondly in deciding whether to draw inferences of fact which are open to you on the evidence which have been given in relation to matters in respect of which the person not called a witness could have spoken.
That is a bit of a mouthful. Let me try and break it down. If you think there is some substance in the argument made by one or either of them in their final address that the other side did not call so and so and you think that they should have called that person because they are in their camp, if I can call it that, then you can infer if you want to - you do not have to but you can infer that person's evidence would not have assisted the party who you think should have called that person.
If you draw that inference you can go on and use that to decide whether or not to accept any other evidence relevant to that person, that has been called in the case, or whether or not to draw an inference about the topic about which the person has spoken.
It is a technique that you are allowed to use. It is not compulsory, you do not have to. You might say to yourself, 'For heaven's sake, we have sat here for seven days, did we really need to hear any more evidence about this case?'. You might be completely unattracted by these arguments put by the barristers that it is a matter of great significance that particular witnesses were not called.
On the other hand, you might think it critical and a real problem for one side or the other that a particular witness was not called. I say to you again, you cannot speculate about what the person would have said, but you can use the failure to call that witness in the way that I have described.