The examining magistrate shall summon before him, by a bailiff or a law enforcement officer, all persons whose testimony he deems useful. A copy of this summons shall be delivered to them.
Witnesses may also be summoned by simple letter, by registered letter or through administrative channels; they may also appear voluntarily.
When summoned or summoned, witnesses are advised that, if they do not appear or refuse to appear, they may be compelled to do so by force majeure pursuant to the provisions of article 109.