Question

who is the witness in the context of criminal justice system​

Answer 1

1. A person who testifies under oath in a trial (or a deposition which may be used in a trial if the witness is not available) with first-hand or expert evidence useful in a lawsuit. A party to the lawsuit (plaintiff or defendant) may be a witness.
2. A person who sees an event
3. A person who observes the signing of a document like a will or a contract and signs as a witness on the document attesting that the document was signed in the presence of the witness.
4. To sign a document verifying that he/she observed the execution of the document such as a will.

Directly taken from Farlex's legal dictionary.

Answer 2

Answer:

A witness is someone who has knowledge about a matter. In law a witness is someone who, either voluntarily or under compulsion, provides testimonial evidence, either oral or written, of what he or she knows or claims to know