The most commonly used defense is denial by the public official that bribery or other corrupt practices took place, often with an emphasis on the 'good' character of the defendant. Sound corroborative evidence is essential in dealing with this defense. In other cases, the official may claim he or she was legally entitled to money received or may deny that there was any connection between a financial benefit and improper use of office. The best rebuttal is evidence that the defendant received a benefit in return for a specific official act. The diminished capacity defense (e.g., because of illness or drug or alcohol use) is best rebutted through testimony by an expert witness for the Government. In cases developed through undercover investigations, the defendant may claim he or she was tricked by an intermediary, was entrapped by outrageous Government conduct, or was conducting a personal undercover investigation. These are best countered by careful use of intermediaries, recordings of conversations, and following Federal Bureau of Investigation guidelines. Defenses in voucher or overtime fraud cases are usually equitable defenses that urge jury nullification and can be countered by reference to written regulations. Finally, the 'attorney's advice' defense can be countered by calling the attorney as Government witness.