Jinn

There are some varying views among ulema on these matters, so if you have a genuine interest in pursuing parapsychology research and would like a solid fiqh view, it is good to sit down with a jurist and discuss your plans.

Hiring someone to perform a work adds another dimension to the fiqh discussion since it falls under the subject of transactions, and so you should discuss whether or not it is considered a legitimate or allowable transaction according to that jurist. There are certainly different scenarios one could envision, e.g. hiring someone who asserts they are psychic and depending on their personal perceptions is a different sort of transaction from hiring someone to operate some sort of sensor equipment or special camera.

There may also be some ethical considerations. For instance, seeing as most human beings do not like to be the subject of scientific research without their permission, possibly some jinns feels the same way. These things might sometimes be discussed as well.

All prayers and du'as are good. Sincerely and wholeheartedly beseeching Allah to assist a person and to seek tawassul of Ahl al-Bayt (A) in helping them is very powerful, for any problem. (This is, of course, for people who agree theologically with tawassul.) 

I am not aware of any classical sources that specifically identify Za'far the jinn as coming to Karbala, although this story became popularized later. However, there are narrations which indicate that some of the jinn sympathized with or sought to aid Imam Husayn (A), and so the story of Za'far the jinn can be seen as reflective of that general idea. 

The Qur'an and hadith (both Sunni and Shi'i) give the sense that the jinn exist in the same world as us. The Qur'an and hadith describe occasional interactions between humans and jinn on a physical level - for instance, seeing a jinn manifest as an animal (as in the story of the jinn who came to see Imam Ali in the Mosque of Kufa) or hearing their voices audibly. Another example would be the jinn working for the prophet Sulayman (A).

However, apart from those occasional interactions, usually jinn keep to themselves and human beings do not see them.

However, some mystics have held that there is a sort of veil between the human world and the jinn world, which you could call the barzakh. That is, humans and jinn subsist in the same realm, but in something akin to parallel dimensions. I am not aware of any basis for this in Qur'an and hadith, but it could be true. 

So do jinn live in the barzakh? To me, the best view is "maybe" and "it depends on what you call the barzakh". If one takes "barzakh" to mean something akin to "mundus imaginalis" - that is, the imaginal realm which humans access through dreams, visions, or imagination, it might be correct to say that jinn live in barzakh. After all, people usually encounter jinn in dreams or the inner realm (for instance, Shaytan whispering to the heart), rather than in physical life. This is similar to how people are more likely to have a dream or vision of a deceased person, such as Imam Husayn (A), rather than physically seeing them walking down the street.

If one takes barzakh to mean specifically the place where human spirits go after death but before the Resurrection... while this meaning of "barzakh" may have some relationship to the above, I am not aware of any texts which specifically say that deceased human spirits live in the same place as living/deceased jinn, although I don't think we have any texts that rule out any sort of interaction ever between living/deceased jinn and deceased humans.

In any case, it seems as if the existence of the human being after death is more similar to the jinn, because the human being in the barzakh is less encumbered by the physical body and able to move around more.

In fact, I don't think we have any texts that say what happens to jinn after they die but before the Resurrection - for instance, do they go to their own barzakh? - however, the Qur'an says that, after Resurrection and Judgment, the jinn who go to Hell and the humans who go to Hell are all mixed together in the same Hell. It does not specify whether the jinn who go to Heaven and the humans who go to Heaven go to the same Heaven.

Anyway, it can be quite difficult to make concrete statements about spiritual cosmology, metaphysical realities, or other things which are not tangible. Even if someone says something, it is really quite difficult to prove whether it is true or false, except in the case of Qur'an and accurate hadith, which we accept on the basis of them being divinely inspired or approved.

So, this, in short, is my understanding of what the Qur'an and hadith say, and also what some mystically inclined thinkers have said. God knows best!