UK - how are jurors replaced after having been dismissed?

Question

In England, after a prospective juror has been rejected (say for cause), how is she or he replaced?

I see from http://www.inbrief.co.uk/legal-system/jury-selection-process.htm# that

The selected jurors are most commonly divided into groups of 15 and then assigned to a court case. The court clerk will select 12 out of the 15 potential jurors at random to sit on the jury. [...] If the courts require the juror to stand down then one of the remaining 3 jurors that was not originally selected will fill the space.

My questions are :

1. Do I understand correctly that a juror is picked at random among the 3 remaining jurors to replace the one that was dismissed?
2. Can this replacement juror also be challenged?
3. What happens if more than 3 juror end up being dismissed? Where do the replacement juror come from then? (subsidiary question: does that ever happen?)
4. Do the parties know anything about the 3 potential replacement jurors, or do the parties know only about the potential jurors currently sitting in the box?

Note : if possible, I would very much appreciate if answers could point to references from official sources.

Hope that's not to many questions at once.

Answer 1

There are two important points you need to consider: jurors cannot be challenged (in the US sense), and the judge has wide discretion to handle any problems that arise in his court.

If a juror has prior knowledge of the case, or could not be expected to be impartial, the judge (or sometimes the bailiff) will excuse him, and bring in one of the three replacements. If either side's lawyers dislike the look of a juror, they may if the judge allows ask questions to elicit such reasons, and then ask the judge to disqualify (I was on a jury where one of my colleagues was a policeman, and the defence suggested that he could not be impartial; the judge asked some questions and then excused him, and I understand he was never actually empanelled that week). But you are not permitted to select jurors you think will favour you or (equivalently) to ask to dismiss a juror without a factual disqualification; you can't, for example, ask about a juror's politics. Disqualifying a juror is thus rare, and the chance of four jurors having ties to a particular case is so remote as to be not worth worrying about.

The second point, and the reason why written authority is hard to find, is that the judge has almost unlimited discretion over any action in his Court that does not infringe statute. There was a case in the newspapers recently where a juror discussed the case he was hearing in the pub, and was therefore dismissed from the jury; the judge consulted prosecution and defence and decided to proceed with eleven jurors rather than start the trial again. This does not mean that 'any trial can be heard with eleven jurors'; it means that in that particular case justice was best served by continuing. There is always the option to request a mistrial (which may or may not be granted) or to say that, a fair trial now being impossible, you intend to appeal on this point; but failing that the judge's decision on any procedural point is binding.