She noted that at the time she was researching and writing, there were errors, or "false rumors," about the incorruptibility of some saints.
Photo quality could sometimes lead people to believe that the "simulated figures" holding the relics of saints were really miraculously preserved corpses, she wrote.
An 18th-century pope gave his definition of incorruptibility in a treatise on the process of beatification and canonization of saints.
Prospero Lambertini, the future Pope Benedict XIV, wrote the lengthy work while serving in the Holy See's congregation for the promotion of saints' causes from 1708 to 1728.
Two chapters of the book, titled "De Cadaverum Incorruptione," outlined the young theologian and lawyer's position on the phenomenon of incorruptibility.
According to Cruz, Lambertini ruled "that the bodies of saintly persons that are found intact, but disintegrated after a few years, could not be considered miraculous preservation."
"The only conservations he was willing to consider extraordinary are those that retain their lifelike flexibility, color and freshness, without deliberate intervention, for many years following their deaths," she noted.
Cruz's book documented cases where this has happened, such as that of St. John of the Cross, who died in 1591 and whose body, she wrote, "is still perfectly supple."
More recent saints have also exhibited this phenomenon, such as St. Charbel Makhlouf, a Lebanese monk who died in 1898.
Other miracles also occured around the time of St. Charbel's exhumation from his dirt grave, a few years after his death. One was the presence of a fragrant scent, a common phenomenon with incorruptibles. A bright light also emanated from St. Charbel's grave after his death, prompting devotees of the holy monk to ask for his remains to be examined.
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A common objection to the belief in incorruptibility is that the body must have been either deliberately preserved, a practice since ancient times, or that the conditions of the grave or tomb allowed for natural preservation.
In at least one case, modern scientific examination has found that a saint previously believed to be incorrupt was likely not.
According to a 2001 article by Heather Pringle, a Church-sanctioned investigation by Italian scientists in the 1980s found that the 13th-century Tuscan saint Margaret of Cortona had received extensive embalming and other intervention after death.
The scientists also uncovered documents which showed that the embalming had been requested by devotees of the saint, a patron of reformed prostitutes. But after the passage of years, the fact had been forgotten, and her appearance led people to believe it was miraculous.
The evidence had been covered by her clothes, and out of a sense of modesty a full examination of her body had not been carried out for centuries.
The same scientists, however, could find "not a trace of human intervention" on another 13th-century saint and well-known incorruptible in Italy, St. Zita.