Explanation:

- Option 1: Void

- A promise to pay a witness anything beyond reasonable expenses for attending a trial is generally void. This means such an agreement lacks legal enforceability. It's meant to prevent any potential bias or influence on the witness's testimony.

- Option 2: Valid

- If a promise to pay beyond expenses were considered valid, it would imply no issues with legality or enforceability, which can lead to potential abuses in influencing witness testimony.

- Option 3: Unlawful

- Terms such as "unlawful" suggest violating statutes or regulations. While paying beyond expenses is void, it is not generally criminal unless it involves perjury or bribery.

- Option 4: Illegal

- "Illegal" implies a breach of law that might attract penalties or criminal charges, such as bribery or corruption. Offering beyond expenses is not typically categorized as outright illegal unless further laws are broken.

Correct Answer: Option 1 - Void