The evocation of spirits is forbidden

[John Wassov]

The evocation of spirits is forbidden

The heavenly religions [according to the Bible and the Quran] prohibit the evocation of spirits and consider it unlawful;

Because some evil genies (: demons) and evil spirits meddle in their evocation; so that a profligate or disbelieving genie (: demon) will come instead of the spirit to be evocated.

http://quran-ayat.com/man/1.htm#Evocation_of_Spirits_

The demon will answer the questions but, together with the correct answers, he will mix some false words: words of infidelity, blasphemy and association [with God.]

E.g. if they ask him about a patient, will he be cured or will he die, the demon will say to them: Take the patient to the shrine of Imam Abbas, the son of Ali, and tie him to the gold cage of his shrine, and he will be cured.

He may tell them the same thing concerning their Christian patrons [like Saint Patrick or Saint Peter] or their Jewish sages or rabbies [like Bar Yohaya or Rachel's tomb.]

Or he may say to them: Sacrifice a sheep for the Imam [the saint or sage], and the patient will be cured, or some other requests that are some sorts of disobedience and association or sharing such imams, saints and sages [with God Almighty: Who is the only Patron.]

However, the person who asks, will believe in the words of the demon; because he thinks, within himself, that the evocated person died and went to the next world or the afterlife, the World of the judgment of truth, so he should not lie to us; he then does not realize that the one speaking to him is a disobedient or sinful demon, and he is not the spirit supposed to be evocated.

[John Wassov]

When some group of people meet for such purpose as the evocation of spirits, and there have been some movement of some objects like letters or cups etc. or voices may be heard --> then almost it is by a living demon, and not by a soul or spirit of a dead man.
This is because the soul cannot move any material object, and cannot speak by any audible voice.

http://quran-ayat.com/man/index.htm#...l_after_Death_