Obviously, the action taken by John and Martha is not good, it's totally unethical. What they are doing is helping the law to punish a person who has not committed the crime. Murder was done by someone else and person getting punishment is the one who has not done the murder. Being socially and ethically responsible citizens, John and Martha should come forward and tell the truth to law enforcing agencies. Since they are the only witness to the murder and the real murderer cannot be disclosed without disclosing their affair, therefore they should disclose their affair for the sake of ...