The question could not be answered with a simple "yes" or "no" without the witness implicitly confessing to the murder.
Compound questions are a common feature in loaded questions such as "Are you still beating your wife?" The argument is phrased as a single question requiring a single answer, but actually involves two or more issues that cannot necessarily be accurately answered with a single response. By combining the questions "Are you currently beating your wife?" and "Have you ever beaten your wife?", one can make it impossible for someone who has never beaten his wife to effectively answer the question, as phrased with a simple "no". Instead all questions must be answered, therefore the innocent man should say "I have never beaten my wife." Thus not only saying no current wife beating is occurring, but none has ever happened.