Excuse: Infancy

At common law, children below the age of seven were deemed doli incapax—irrebuttably presumed to be incapable of forming criminal intent and therefore immune from prosecution for a crime. Children between the ages of seven and fourteen were presumptively doli incapax but that presumption could be rebutted by "very strong and pregnant evidence" by the state that the child had the "discretion to judge between good and evil" and "understood what he did" (Hale, pp. 26–27). According to William Blackstone, the infancy defense reflected both a judgment about the impropriety of exacting punishment upon those who were not responsible for their actions and the practical consideration that categorically immunizing all children from prosecution could "propagat[e] a notion that children might commit . . . atrocious crimes with impunity" (pp. 22–24). The infancy defense was carried over into the criminal law of the United States along with other traditional concepts of English law, and it shaped the course of early prosecutions of children. Several states codified the doctrine in their penal codes.

The chronological distinctions drawn by the infancy defense comport (albeit, not neatly) with classic social scientific theories about child development and maturation, particularly the works of Anna Freud and Erik Erikson on children's mental functioning and the works of Jean Piaget and Lawrence Kohlberg on children's moral growth. Current psychological research on children's maturity and mental capacity supports the view that "decision-making capacities increase through childhood into adolescence and that, although there is great variability among individuals, preadolescents and younger teens differ substantially from adults in their abilities" (Scott and Grisso, pp. 137, 157).