@clay A couple of points on the actual idea (I may address some of the points from the ensuing discussion between you two later):
When I said about keeping people in a bubble, you quickly corrected me. I just had another look, and I think it was this bit that made me think of a bubble:
A controlled environment that protects jurors from external influence and manipulation
I presume then that this doesn't refer to their environment the whole time, but just when they're involved in the process - e.g. interrogating the candidates.
In any case, I think that while being able to directly interrogate candidates, rather than just getting stuff from a potentially biased media, is a good thing, I do also think it would be bad to stop them getting information from other sources, even if some or all of those sources may be biased. Some candidates will simply be better at presenting themselves, and being a slick speaker does not necessarily translate into being a good representative.
The manifesto does actually talk about expert testimony, but I can't see this being given more detail in terms of how that would work.
On sampling - random sampling obviously makes the most sense on the surface, but given the discussion that has taken place, I might address that in a separate post.
As for the idea as a whole, it's clear that informed representative sample of voters should make a better decision than the population as a whole.
However, you might consider this to be to be a slightly "philosophical" or "meta" point, but does educating and making competent the sample change its nature and stop it from being representative? The manifesto made it clear that selecting people based on competence would create a biased sample. But what are competent people other than people who were once incompetent and educated out of it?
Finally for this post, while this might give a better result within the landscape of a given election, it changes the landscape itself, which could lead to unintended consequences. The vast majority of people would never vote in an election, and they might view that negatively, with further consequences from that. Perhaps you would argue that it doesn't matter if they disengage from politics because we only need to jury to be engaged, but I think there's something a bit degenerate about a wider public that takes no interest in what their elected representatives are doing.
I have previously discussed advantages of lottery-based methods (variations on random ballot, essentially), but at least in these methods everyone gets to vote, even if most of those votes don't do anything. (This is specifically on the subject of disengagement.)