Aside from legal considerations as to the knowing or voluntary nature of a plea, there are other restrictions or prohibitions on the opportunity to plea bargain. In federal practice, U.S. attorneys may not make plea agreements which prejudice civil or tax liability without the express agreement of all affected divisions or agencies (USAM 9-27.630). Moreover, no attorney for the government may seek out, or threaten to seek, the death penalty solely for the purpose of obtaining a more desirable negotiating position for a plea arrangement (USAM 9-10.100). Attorneys are also instructed not to consent to “Alford pleas” except in the most unusual circumstances and only with the recommendation of assistant attorneys general in the subject matter at issue. In any case where a defendant has tendered a plea of guilty but denies that he or she committed the offense, the attorney for the government should make an offer of proof of all facts known to the government to support the conclusion that the defendant is in fact guilty (USAM 9-16.015). Similarly, U.S. attorneys are instructed to require an explicit stipulation of all facts of a defendant’s fraud against the United States (tax fraud, Medicare/Medicaid fraud, etc.) when agreeing to plea bargain (USAM 9-16.040).