witness vs lay witness

witness and lay witness both are nouns.

Word	Noun	Adjective	Verb	Adverb
witness	Yes	No	Yes	No
lay witness	Yes	No	No	No

As nouns, lay witness is a hyponym of witness; that is, lay witness is a word with a more specific, narrower meaning than witness:

witness (noun)	lay witness (noun)
testimony by word or deed to your religious faith	any witness who does not testify as an expert witness
someone who sees an event and reports what happened
a close observer; someone who looks at something (such as an exhibition of some kind)
(law) a person who attests to the genuineness of a document or signature by adding their own signature
(law) a person who testifies under oath in a court of law

witness (verb)	lay witness (verb)
be a witness to
perceive or be contemporaneous with