The Official Website for The G.A. Wahid Khorasani

647. It is forbidden to dig open the grave of a Muslim, even if he be a child or insane. However, if his body has disintegrated, and his bones have turned into dust, there is no problem in doing so.

648. It is forbidden to dig open the grave of the descendants of an Imam, the martyrs, the scholars, and other people, digging whose graves would be disrespectful, even though many years may have passed (after their burial).

649. It is not forbidden to dig open a grave in the following cases:
1. The body is buried on usurped land, and the owner is not pleased to let it remain there.
2. The shroud or any other thing that is buried with the body, is usurped, and the owner is not pleased to let it remain in the grave.
The same will also apply if something from the deceased’s wealth which is passed on to his inheritor, is buried with him, and the inheritor is not pleased to let the thing remain in the grave, unless the thing is of insignificant value. In this case, digging open the grave is problematic.
3. The deceased is buried without performing ghusl on his body, or shrouding his body, as long as digging open the grave is not a sign of disrespect to him. The same will also apply if it is later realized that the ghusl was invalid, or if the body was shrouded in a manner not prescribed by the sharia, or if the body was laid in the grave without making it face the qiblah.
4. The body needs to be examined to establish a right which is more important than the honor of the deceased.
5. The body is buried in an area which amounts to disrespecting the deceased, such as the cemetery of the kÁfirs, or a landfill.
6. The grave needs to be dug open for a canonical issue which is of more importance than exhumation. For example, delivering a baby that is alive from the womb of its mother, after the mother has been buried.
7. If there is a fear that scavengers may tear apart the deceased’s body, or the grave may get flooded, or an enemy may exhume the body.
8. A part of the deceased’s body needs to be buried along with the rest of his body. The obligatory precaution is that the part should be buried in a manner that the rest of the body is not exposed.