Investigatress

As many of these are microscopic, a most promising field will, without doubt, open to the investigators and investigatresses who shall enter therein.

Source: wiktionary

La reine mit les pistolets à part avec la lettre, en attendant mieux; c’était un commencement d’indice qui pouvait conduire à la vérité.

Source: wiktionary

An “investigatress” comes to the institution and endeavors to prove the knight errant a thief. […] Maude Raymond as the investigatress does a most laughable imitation of Mrs. Fay, and made a decided appeal to the audience in several “coon songs.”

Source: wiktionary

But the result of my study of the unaccountable beings of my own age is the belief that each of them puts her suitors to some same test. The suitors may never perceive what the test is: the investigatress knows admirably.

Source: wiktionary