Is it permissible for women to veil themselves from their untrustworthy mahrams, such as one whose harassment is feared?

If a person's natural disposition (fitra) has been corrupted by forbidden acts, or if he displays behavior that places him under suspicion, a woman should treat him as a stranger (ajnabi). Therefore, it is not permissible for him to be in seclusion with her, shake her hand, or speak to her except in a customary and appropriate manner. She must also observe hijab in front of him. Jurists have explicitly stated that if there is fear of temptation (fitna) from a mahram (a close relative with whom marriage is forbidden), she becomes like a non-mahram (ajnabiyyah) to him, as a preventative measure to close the door to temptation. Furthermore, looking or touching with lust is a type of zina (fornication/adultery), and its prohibition is more severe when it involves mahrams. Neither he nor she is permitted to expose themselves to what is forbidden.