witnesser vs attester

witnesser and attester both are nouns.

Word	Noun	Adjective	Verb	Adverb
witnesser	Yes	No	No	No
attester	Yes	No	No	No

As nouns, attester is a hyponym of witnesser; that is, attester is a word with a more specific, narrower meaning than witnesser:

witnesser: someone who sees an event and reports what happened
attester: someone who affirms or vouches for the correctness or truth or genuineness of something

Other hyponyms of witnesser include attestant, deponent, deposer, testifier.

witnesser (noun)	attester (noun)
someone who sees an event and reports what happened	someone who affirms or vouches for the correctness or truth or genuineness of something