Permissibility of talking about a Muslim in his absence

Q 2: What are the situations in which it is permissible to speak about a Muslim brother in his absence without committing Ghibah (backbiting)?

A: Ghibah (backbiting) means that a Muslim mentions the defects and shortcomings of his brother (in religion) which he does not like. However, there are certain situations in which scholars permit a Muslim to speak about his brother for the public interest. Some of these situations are: Speaking out against the injustice done to oneself such as saying to the judge or ruler that so and so wronged him by doing such and such; or asking for a Fatwa (legal opinion issued by a qualified Muslim scholar) such as saying to the Mufty (Islamic scholar qualified to issue legal opinions) so and so did such and such; is he right or wrong? Some of them are also warning Muslims against people of evil and suspicion, such as Jarh (criticism of Hadith narrators) and asking for advice when intending to get married to the daughter of someone or entering into partnership or living near someone. Some of which are also mentioning the acts the Fasiq (someone flagrantly violating Islamic law) does openly in public. Added to that: Defining someone in a way that does not intend defaming him as being known as the Blind, Lame, Deaf and the like.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.