godan verb (-su), transitive verb
ascertain; confirm; verify; make sure of
Used for investigating or checking facts, often in formal or careful contexts. Commonly appears in compounds like 聞きただす (to inquire closely).
See also: 聞きただす (ききただす)
The police are ascertaining the truth of the case.
彼の言い分をただす必要がある。
We need to verify his account.