Question: One of my friends starts barking like a dog (I am not joking) when he hears another dog barking. People think that he has a Jinn in his body As a Muslim we all do believe that Jinn exist. My question is: Can they enter and possess a human being? 
    Answer: Yes, as Muslims we do believe that the Jinn exist even though we are not able to see them. The reason is that the Qur’an has told us that the Almighty has created them. In fact, the Qur’an says that the Almighty created the Jinn from fire (55:15). It also says that the Satan who enticed Adam was among the Jinn (18:50). We are further told by the Qur’an (7:270) that the Jinn are able to see human beings while the reverse is not true. Likewise, the Qur’an (6:130) informs us that the Almighty has sent Prophets among the Jinn just as He has done so among human beings, which clearly points to the fact that, like human beings, the Jinn will also be held accountable for their deeds before the Almighty. Similarly, there are certain other details which the Qur’an mentions about the Jinn. However, nowhere does it give us any information on the issue you have inquired about. Authentic Ahadith are also silent on this matter.
    Therefore, we must rely on our own observation and data in order to form an opinion on this issue. If one is able to scientifically establish that a Jinn can do such an act, only then should a definite verdict be given in this regard. 
    However, in most cases which are reported in this regard, the patient generally suffers from hysteria and certain other psychological diseases – which can be cured if proper treatment is given and instead of hunting for witch doctors, one is wise enough to look for good psychiatrists.