A postulator is the person who guides a cause for beatification or canonization through the judicial processes required by the Catholic Church.
The qualifications, role and function of the postulator are spelled out in the Norms to be Observed in Inquiries made by Bishops in the Causes of Saints, which has been in effect since 7 February 1983.
[1] A petitioner seeking the beatification may appoint as postulator anyone, cleric or not, who is an expert in theological, canonical and historical matters, and versed in the practice of the Congregation for the Causes of Saints, subject to the approval of the bishop.
[5] Like all officials who take part in a cause, the postulator is obliged to take an oath to fulfil his duty and to observe the strictest confidentiality.
[6] A postulator, instructed by the petitioner, initiates a cause by presenting to the bishop of the diocese where the candidate for beatification died, a written petition with supporting documentation.