Is it permissible to swear falsely upon the Quran to protect oneself and out of fear for one's life, as in the case of a witness to a shooting who faces threats from one of the perpetrators to prevent him from giving his true testimony?

If a witness fears harm or injustice befalling them, they are not obligated to give testimony. If they are compelled to give false testimony, and the harm inflicted upon them is severe, such as death or the loss of a limb, and they strongly believe that theener is capable of carrying out their threat, and they find no way to prevent the harm except by bearing false witness, and this does not lead to the taking of a life or an assault on honor, then they are excused for bearing it. There is no blame in swearing a false oath under duress if the conditions of duress are met.