Certifiably

Tobias was certifiably insane.

Source: tatoeba (11667681)

Was the accused at the time of the commission of the act with which he is charged, and before that time, laboring under such mental disease as to render him certifiably insane? […] He goes on to ask, How is a jury to determine whether a man is " certifiably insane?" How is any man to attach a definite meaning to "certifiably insane?" "The phrase can only mean that a couple of doctors can be found to certify that in their opinion the man is insane."

Source: wiktionary

Must such a neighborhood or district maintain a certain percentage of certifiably ethnic residents to maintain its eligibility?

Source: wiktionary

One or two were hurriedly fetching ropes and yelling contradictory orders, from which I deduced that Mr. Brown had indeed fallen into the gorge, but was not yet certifiably dead.

Source: wiktionary