It is permissible to speak negatively about a person:
(1) to help the person, or
(2) to help anyone victimized by the person, or
(3) to resolve major disputes, or
(4) to enable others to learn from the mistakes of that person, provided that:
(1) one’s remarks are based on first-hand information and careful investigation, and
(2) it is apparent that this person is wrong, and
(3) the person has been spoken to but refuses to change his behavior, and
(4) the statement to be made will be true and accurate, and
(5) the intent of the speaker is for a constructive purpose only (and there is a reasonable chance that the intended goal will be accomplished), and
(6) there is no alternative means by which to bring about the intended result, and
(7) no undue harm will be caued by the statement.

The illustrations presented below (as well as those to be dixcussed in the section on rechilus {gossip} serve to clarify the application of these conditions.

Sefer Chofetz Chaim, 20 Cheshvan, page 148

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