expression, i-adjective
innocent; not guilty; harmless
Used for a person who is not guilty of a crime or wrongdoing, or for an action/thing that is harmless and without ill intent. Often used in legal or moral contexts.
彼は罪がないと主張した。
He insisted that he was innocent.
その冗談は罪がないから気にしないで。
That joke is harmless, so don't worry about it.
無罪 is a noun meaning 'innocence' or 'not guilty' in a legal sense, while 罪がない is a more descriptive phrase that can also mean 'harmless' in everyday contexts.
Phrase composed of 罪 (crime, guilt) + が (subject marker) + ない (not exist). Literally 'there is no guilt'.