WordNet: informant, witness, witnesser

someone who sees an event and reports what happened

• hypernym beholder, observer, perceiver, percipient

• hypernym speaker, talker, utterer, verbaliser, verbalizer

• hyponym attestant, attester

• hyponym deponent, deposer, testifier

informant

• (englanti) inform (derivationally related)
• (suomi) informantti (synonyymi)

witness

• (englanti) witness (derivationally related)
• (suomi) silminnäkijä (synonyymi)

witnesser

• (englanti) witness (derivationally related)
• (suomi) todistaja (synonyymi)