Who has more right to her son – her or her husband whom she suspects of witchcraft? What are the signs of the practitioner of witchcraft?
Question

                My son is nearly 11 years old. He has become very aggressive; he does not respect me and shouts at me. Sometimes even he uses his hands without any justifications, after his father gave him a computer as a gift. His father deals by sihr, I do not know if he is sahir himself or not, Allah alone knows. He wants to take my son from me (as we are divorced). 

How can I protect my son and myself? What can I do so that my son returns to how he was before? How can I know the reality of his father? In the case that I make sure he is a sahir and wants to harm me and my son, am I permitted to not let him see our son if he wanted to?.
Praise be to Allah.Firstly:  
Islam enjoins parents to 
    take care of their children and raise them well. Children will grow up on 
    what they hear, read and see in their home, on the streets and in school, 
    and whatever faults happen in their upbringing are because of faults in one 
    or  all of these aspects. 
What has happened with your 
    son, of his bad attitude towards you, may because of what he has seen and 
    heard at home of the problems between you and your husband, which led to 
    divorce, or it may be because of the influence of what he has seen and read 
    on the computer, or it may be the result of witchcraft done against him by 
    his father in order to take him from you. Any of these things is possible, 
    or it may be all of these reasons combined that has lead to this bad 
    behaviour of your son towards you. 
Whatever the case, you have 
    to set things straight by looking for the causes that have led to these 
    problems, so that you can deal with the matter by dealing with the cause. If 
    it is because of your problems with his father, then you must make him 
    understand the reality of the situation and what happened [?} between you, 
    in a way that is appropriate to his age and level of understanding. If the 
    cause is what he hears, watches and sees on the computer then you must keep 
    an eye on whatever he is looking at, and it is essential to teach him to 
    make good use of the computer. If he does not respond, then you can forbid 
    him to use it altogether. If the cause is his father doing witchcraft on 
    him, then you can start to remedy it by using shar’i ruqyahs from the 
    Qur’aan and saheeh dhikrs of the Prophet  (peace and blessings of Allaah 
    be upon him). There is no reason why you shouldn’t take him to someone whose 
    religious commitment you trust, to treat him in the shar’i manner for such 
    cases. 
Secondly: 
You can find out whether 
    his father is really doing sihr (witchcraft) by finding out how he treats 
    others or what he really says to those who visit him and consult him. 
Some of the scholars have 
    mentioned the signs of the saahir (practitioner of witchcraft) by means of 
    which anyone can discern the saahir from those who are good and righteous. 
    These signs are: 

    1.He asks the sick person for his 
    mother’s name, and some personal possession of the one for whom treatment is 
    sought, such as his hair or clothing.

    2.He mumbles words that have no 
    meaning and that the listener cannot understand. The muttering may be calls 
    to the jinn or devils to come and serve him.

    3.Another sign is that the saahir 
    does not attend Jumu’ah prayer or the five daily prayers in the mosque.

    4.He is dishevelled and smells 
    bad, and he likes being in the dark and on his own.

    5.He gives the sick person an 
    amulet (“hijab”) containing some mumbo-jumbo, squares or numbers.
To find out the truth, he 
    should have all or some of the characteristics. Thus you will know the truth 
    about him. It should be noted that you may be exaggerating in suspecting him 
    of witchcraft. You have to be fair in judging him, and fear Allaah before 
    making accusations and claims of which he is innocent. 
But so long as you have 
    separated from him, we do not think that you should concern yourself too 
    much with your ex-husband and whether he is a saahir or not; rather what you 
    should do is focus on how to protect yourself and your son, and how to 
    fulfil your duty of raising this boy. 
Thirdly: 
With regard to custody of 
    the child, it is known that the purpose of custody is to protect and take 
    care of the child. Hence a person’s right to custody is waived if he is 
    immoral or corrupt, or if he neglects him, or if he travels a great deal, 
    which would harm the child’s interests. 
Shaykh al-Islam Ibn 
    Taymiyah (may Allaah have mercy on him): 
It should be noted that 
    there is no text which gives precedence to either parent in general terms, 
    or chooses one of the parents in all cases. The scholars are unanimously 
    agreed that neither of them is specified in all cases, rather when there is 
    transgression of the limits or neglect, precedence is not to be given to the 
    one who will be like that (i.e., the parent who will transgress the limits 
    or be neglectful) over the one who is just and good and will do what is 
    required. 
Majmoo’ al-Fataawa 
    (34/132). 
It should be noted that the 
    period of custody extends until the child reaches the age of discernment and 
    independence, i.e., custody lasts until the child is able to discern and is 
    independent of his guardian, in the sense that he can eat and drink by 
    himself, and clean himself after going to the toilet by himself, and so on. 
As he has reached the age 
    of 11, he should be given the choice of living with his father or with you, 
    so long as the choice is made by him freely, without any pressure or 
    compulsion, and so long as the reason for his choice is not that he will 
    never be told to pray or obey Allaah, or to do anything that is in his 
    religious or worldly interests, because his choice in this case would be 
    harmful to him. Many children care only about choosing the one who will 
    spoil them the most or give them the toys and games that they want, so in 
    that case he should not be allowed to have what he wants. 
If it is proven that his 
    father is engaging in witchcraft, then it is not permissible for him to take 
    his son, rather he should be withheld from him until he repents sincerely to 
    Allaah. 
If it is not proven that 
    the father is engaging in witchcraft, then the parents should cooperate in 
    raising their son, and pay attention to what is in his best interests, so 
    that their conflict will not be a cause of the children failing and being 
    lost. 
See also the answers to 
    questions no. 8189 and 
    20705 and 
    21516. 
We ask Allaah to set all 
    your affairs straight and to guide your son to that which our Lord loves and 
    is pleased with, and to set his father straight and protect his religious 
    commitment. 
And Allaah knows best.