The federal government established the U.S. Court of Appeals in 1838, after designing a separate criminal court in the District of Columbia. This court consisted of one judge with the right to appeal to the circuit, or full court. By the late-1940s, the number of Appeals Court Justices had increased to nine. Heavy caseloads and increased presidential appointees necessitated updated facilities.
Several important appeals have come before the U.S. Court of Appeals for the District of Columbia. The court heard the 1949 appeal of "Axis Sally ," a woman convicted of treason by the U.S. District Court. The circuit court affirmed that Axis Sally did commit treason when recording a Nazi propaganda radio show to be broadcast over American radio lines. Furthermore, the court held that Axis Sally had no right to avoid U.S. prosecution by remaining in Germany; that a treason can be committed by American citizens residing in enemy countries; and that she committed treason by breaking her allegiance as an American national.
In the 1953 Hurd v. Hodge, a racial discrimination case, the court also upheld the lower court's decision that allowed property covenants to discriminate against African-Americans. (The U.S. Supreme Court later overturned this decision.) In a series of cases tried from 1954 until 1967, the court shaped the definition of insanity as it related to judicial cases. The court heard Durham v. Unites States in 1954. Here, city prosecutors charged defendant Monte Durham with housebreaking, but his attorney challenged the existing definition of insanity used by the court. Durham pleaded that "existing tests of criminal responsibility are obsolete and should be superseded." The court reviewed the case and issued a ruling, which stated that a plea of insanity would prevail only if the defendant's unlawful act was the product of a mental disease or mental defect. This revised traditional definitions of insanity, which allowed for acquittal if the defendant was so disabled they had no cognizance of the wrongful act; a definition that dated from the M'Naghten case of 1843. With the 1959 Carter v. United States, the court further clarified its stance on insanity pleas, and stated that one's mental disease must directly relate to the unlawful act, and that mere existence of the disease would not merit acquittal.
The court later addressed the issue of expert testimony as related to insanity defenses. In the 1962 McDonald v. Untied States, the court discussed the distinctions between legal and medical definitions of insanity. For the purposes of criminal responsibility, they defined a mental disease as "any abnormal condition of the mind which substantially affects mental or emotional processes and substantially impairs behavior controls." The court reportedly derived this definition to reduce confusion among jurors. In the 1967 case Washington v. United States, the court prohibited the use of expert testimony to avoid complicated technical jargon that served to preplex jurors.