The legal term was peine fort et dure (French for “strong and hard punishment”) and was long established in English common law at the time of the Salem trials as a method of torture to force a mute defendant to enter a plea.
Prisoners accused of capital offenses would often refuse to enter a plea; if they pleaded guilty and were executed, their property would be seized by the Crown and their heirs would receive nothing. By refusing to plead - and thereby refusing to acknowledge the court’s jurisdiction over them - the accused’s heirs would still inherit the estate. Peine fort et dure was the court’s way of coercing a plea.
The aforementioned video is rather grainy and detail is hard to discern. If you’re interested, then to save yourself from the better part of ten gruesome minutes, I provide the following description, selfless masochist that I am:
The video documents the stoning of four persons in what appear to be two separate events, perhaps sequentially and/or at the same location. In each, two victims’ hands are bound, they are wrapped completely in a white sheet and are buried, with perhaps a meter between them, up to an area between the solar plexus and the shoulders. Dirt is filled in around them but not packed in; the victims have a very small degree of movement limited to their head and shoulders.
The crowd backs away to form an uneven circle around the victims, I would estimate less than two meters in some places from the victims. Stones are thrown, and blood is visible on the sheets, and the victims can clearly be seen writhing in pain. As the execution proceeds, the white sheets covering the heads are invariably stripped away by the force of the strikes, quickly revealing the victims’ bloody upper body. Some victims appeared to quickly (< 2 mins) fall unconcious; one of the victims in the second round of the execution was clearly still (somewhat) concious for the better part of the whole ordeal. At one point, he manages to extricate part of his upper body from the hole and appears to be struggling to escape, when several men from the crowd step into the circle, run up to the struggling victim, and throw stones from point-blank range.
Thus any rules regarding the distance from which one must throw the stones would appear to be somewhat less than rigid. Also, the victims were dead long before enough of a pile of stones had accumulated to threaten their air supply: I’d be hard-pressed to think of any cause of death other than trauma or blood loss. The second half the of video cuts out the crowd noise and replaces it with a second-rate folk song that ridicules Islam (the title of the video is “Islam: ‘Religion of Peace’”).