Incorruptibility is a Roman Catholic and Eastern Orthodox belief that divine intervention allows some human bodies (specifically saints and beati) to completely or partially avoid the normal process of decomposition after death as a sign of their holiness.
Incorruptibility is thought to occur even in the presence of factors which normally hasten decomposition, as in the cases of saints Catherine of Genoa, Julie Billiart and Francis Xavier.
In Roman Catholicism, if a body is judged as incorruptible after death, this is most often seen as a sign that the individual is a saint. Canon law allows inspection of the body so that relics can be taken and sent to Rome. The relics must be sealed with wax and the body must be replaced after inspection. These ritual inspections are performed very rarely and can only be performed by a bishop according to the requirements of canon law. A pontifical commission can authorize inspection of the relics and demand a written report. After solemn inspection of the relics, it can be decided that the body is presented in an open reliquary and displayed for veneration. Catholic law allows saints to be buried under the altar, so Mass can be celebrated above the remains.
The remains of Bernadette Soubirous were inspected multiple times, and reports by the church tribunal confirmed that the body was preserved. The opening of the coffin was attended by multiple canons, the mayor and the bishop in 1919, and repeated in 1925. However, the face and hands were covered with a wax mask.