Synonyms for Depone:

n.

witness, testify, law, take the stand, attest, bear witness. depone (noun)
depose, swear.

v.

communication (verb)
depose, swear.
testify (verb)
bear witness, witness, attest, swear, depose.

Other synonyms:

attest, testify. Other relevant words:
witness, testify, depose, take the stand, attest, bear witness.