A witness is a person who is present at and observes a transaction.

Explanation

(English-origin maxim.) A witness is one who was present and perceived the transaction firsthand; this definition excludes those who merely heard about the event or arrived after the fact.

Where this applies

• A man testifies that the defendant confessed to him, but he admits he wasn't present when the events actually occurred — he's not a witness to the transaction, just a hearer of hearsay.
• A woman is called to testify about a car accident she saw happen right in front of her — she qualifies as a witness because she was present and observed the event firsthand.
• Someone offers to testify about what a company's internal meeting decided, but he wasn't in the room — he only heard about it later from a colleague, so he's not a witness to the transaction.