Great posts laying out the rules of evidence.
But I disagree with this conclusion:
What circumstantial evidence does he have? Well, here I think his case is actually the weakest. You will try and rely on circumstantial evidence to establish that although you don’t have direct evidence, there is no other way that the relevant circumstances could have occurred. But in this case the Mirror was able to establish (in relation to I think every single article but one?) that Harry relied on that there was another, public, source for the story, and not hacking a voicemail. That’s not helpful to him at all.
I think this is where his case is strongest. The journalist who testified unwillingly was not a convincing witness, and was unable tp explain the sources in a number of stories. I found it striking that with respect to one particular story, she claimed the source to be Piers Morgan, who has, as we know, refused to testify in this case.
My memory is that there were also a number of invoices to a known hacker that were linked to the stories, and she could not explain what the invoices related to. There was some incredulity, as I recall, that she appeared to have expressed no curiosity at all about what these invoices related to.
I found the question from the judge about why the journalists were not testifying to be particularly interesting, especially as related to Piers Morgan. And this is where Harry's often repeated response of "you have to ask the journalists" is helpful: he was asking the judge to draw adverse inferences from the fact that they chose not to testify, and the one who did so did so under protest. If indeed, everything on all the stories was above board, why would they not have testified. That they didn't is as relevant as the fact that the one who did testify not only testified under protest, but contradicted her own witness statement.
Yes, you are right that the burden of proof is with Harry to establish a prima facie case. But if he can succeed in showing that just one or two of the stories could not have been from the sources claimed by the defence, he will, on a balance of probabilities succeed in his claim.