It is not possible for any person to evoke the spirits of the dead. After leaving the body, spirits are transferred to their lives in the grave where they are either in bliss or distress. They are too busy with their own affairs to respond to conjurers. The spirits of martyrs are placed inside green birds and they roam the gardens of Paradise, eating from its fruit, drinking from its rivers and resting on lanterns fixed to the throne of Allaah, The Almighty. [At-Tirmithi, An-Nasaa'i, Ibn Maajah, Ahmad & Ad-Daarimi] 

Allaah The Almighty informs us that He causes the souls to die (during their sleep) and keeps the ones for which He has decreed death. Allaah The Almighty Says (what means): {Allaah takes the souls at the time of their death, and those that do not die [He takes] during their sleep. Then He keeps those for which He has decreed death and releases the others for a specified term.} [Quran 39:42] Thus, what these 'spiritualists’ claim is either an outright lie in which they use psychological insinuation, different stimuli and scientific trickery, or it is done using Jinns and Devils, which is most likely. Mr. Muhammad Muhammad Husayn has unveiled many of their tricks and deception. Similarly, Mr. Ahmad ‘Izzudeen Al-Bayaanooni has unearthed the lies and fraud committed these by so-called spiritualists. He related a personal experience and incidents that happened to others as well. They all prove that the evoked spirit is no more than a devil assuming the image of the dead person. Perhaps that devil was the Qareen of the deceased (companion from the Jinn who accompanied him in his lifetime). For that reason, it is not difficult for him to answer the questions asked by relatives or friends. Jinn, in fact, possess scientific abilities and general capabilities that humans do not have. Thus, a devil can answer some scientific questions which may impress those who attend such sessions. Dr. ‘Umar Sulaymaan Al-'Ashqar, may Allaah preserve him, listed the names of some famous spiritualists whom the devils deserted, so they became normal human beings again, unable to communicate with Jinn or evoke the spirit of any person, as they once claimed to do. 

Allaah Knows best.