Who is trustworthy?

Hi,

In the Jewish legal system, we only trust someone for matters of Jewish law if that individually is personally observant of Jewish law. [There are nuances in cases in which an individual violates only particular laws, or violates Jewish law only in private.]

Theoretically, one could trust someone who was not personally observant of Jewish law, if one knew through long-term experience with this person that he never lied, regardless of his own good. However, this would require intimate knowledge of the person over an extended period of time, with recent information as well as knowledge of his behaviour in the past.

(Rav Moshe Feinstein, Igrot Moshe Yoreh Deah 2:43)

Have a great day,
Mordechai