Final answer:
An official certificate could be rendered invalid if the notary's term was expired at the time of issuance, which is the most clear-cut reason among the ones provided that would affect the validity of the certificate.
Step-by-step explanation:
The validity of an official certificate issued by a notary public can be influenced by several factors. Among the defects listed, the one that would most clearly render a notarial certificate invalid is if the notary was expired at the time of issuing the notarial certificate. When a notary's term has expired, they no longer have the authority to perform notarial acts, and any such acts they do perform, including the issuance of notarial certificates, would be considered invalid.
Regarding the misspelling of the notary's name on their identification card, this would generally not invalidate the notarial act unless it throws into doubt the identity of the notary or their authority to act. Finally, the failure to file an official oath could potentially invalidate the notarial act, as the oath is a requirement for the notary to be duly authorized to perform their duties. However, this might depend on specific state or jurisdictional laws governing notarial acts.
Therefore, of the options provided, the expiration of the notary's term (Option 1) is most clearly a defect that would render a notarial certificate invalid.