witness
person who can attest to the reality of a fact
expert witness
someone with specialised knowledge who testifies in court
Crown witness
someones who has turned state's evidence
wedding witness
person acting as a witness at a wedding
Two witnesses
Two prophets in the Book of Revelation
contemporary witness
for law, use eyewitness
hostile witness
witness at trial whose testimony on direct examination is either openly antagonistic or appears to be contrary to the legal position of the party who called the witness