Which type of defense encompasses arguments that an individual cannot be made responsible for their actions due to their age?

The correct answer pertains to the concept of "defense of infancy," which addresses the legal principle that individuals below a certain age, often defined by statute, are not considered capable of having the mental capacity to understand the consequences of their actions. This means that minors may not be held fully accountable for criminal actions due to their inability to form intent in the same way adults can. The defense of infancy is rooted in the belief that children are less mature and therefore less responsible for their behavior.

In contrast to this, the other defenses listed do not specifically relate to the capacity based on age. The defense of justification centers on the principle that an act may be deemed legally permissible under certain circumstances, while the defense of necessity argues that an individual acted to prevent a greater harm. The defense of excuse involves claims that a defendant should not be held responsible for their actions due to some personal disability or circumstance, but it does not specifically address age-related incapacity.

Hence, the defense of infancy is distinctly applicable when considering the inability of a minor to fully comprehend their actions, making it the correct choice in this context.