Uncovered by a local paper 2 days ago (article in French).
In Québec at least, jurors are supposed to be anonymous. Lawyers have access to a large list of names at the beginning of the selection process, but that list is taken away afterwards. Once the jury is selected, lawyers are not allowed to know the jurors’ names and details. The judge refers to them by number. Nobody can take pictures of the jury box.
Smartphones are allowed in the courtroom (no ringing, no pictures, etc.). Many of these have Facebook installed.
Facebook can suggest friends based on the fact that they spend a lot of time in close proximity.
So, after a few days of trial, the lawyer or one of their associates, having spent a lot of time in the same room as the jury, can go into Facebook’s “People you may know” section and look for the faces of the jurors. They can then find out their names and occupations, and then use other tools to dig into their past and look for ways to influence them, or to disqualify them.