Situations in Which Gheebah (“Backbiting”) is Permitted

The
scholars have stated that gheebah is permitted in certain situations: 

1-

Complaining. It is permissible for the one who has been wronged to complain
to the ruler or judge and others who have the authority or ability to settle
the score with the one who wronged him. 

2-

Seeking
help to change evil and bring the sinner back to the right path, so he may
say to the one who he hopes is able to do something: “So and so is doing
such and such; tell him not to do it.” 

3-

Seeking
advice or a fatwa (religious ruling), by saying to the mufti (scholar), “So
and so/my father/my brother has wronged me by doing such and such, does he
have the right to do that? How can I solve this problem and ward off his
harm from me?” 

4-

Warning
the Muslims of someone’s evil, such as highlighting the weakness of some
reporters or witnesses or authors. That also includes seeing someone buying
faulty goods, or someone keeping company with one who is a thief or
adulterer, or giving a female relative of his to such a man in marriage, and
the like. You should tell them about that by way of sincere advice, not with
the aim of causing harm and spreading mischief. 

5-

If a
person openly commits evil or follows bid’ah (innovation), such as drinking
alcohol and seizing people’s wealth unlawfully, it is permissible to speak
of what he is doing openly, but it is not permissible to speak against him
any other way, unless it is for another reason.  

6-

For
identification, if someone is known by a nickname such as the dim-sighted
one, or the blind man or the one-eyed or the lame one, it is permissible to
identify him as such, but it is haraam (impermissible) to mention that by
way of belittling him, and if it is possible to identify him in some other
way, that is better. 

It says
in Fatawa al-Lajnah al-Daimah li’l-Ifta: Speaking about a person in his
absence is permissible in certain situations as indicated by shar’I Islamic
legal) evidence, if there is a need for that, such as if someone consults
you about arranging a marriage to him, or entering into a business
partnership with him, or if someone complains to the authorities to put a
stop to his wrongdoing. In that case there is nothing wrong with saying
things about him that he may not like to be said, because there is an
interest to be served by that. One of the scholars summed up in two lines of
poetry the situations in which it is permissible to talk about a person in
his absence, and said: 

Criticizing is not gheebah in six (cases) – complaining, identifying,
warning,

When the
person is committing evil openly, when advice is sought, and when one is
asking for help in removing an evil. 

End
quote. 

And
Allah knows best.