certify

provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes; "His high fever attested to his illness"; "The buildings in Rome manifest a high level of architectural sophistication"; "This decision demonstrates his sense of fairness"

guarantee payment on; of checks

authorize officially; "I am licensed to practice law in this state"

guarantee as meeting a certain standard; "certified grade AAA meat"

declare legally insane