  Robots operating in close proximity to humans rely heavily on human trust to
successfully complete their tasks. But what are the real outcomes when this
trust is violated? Self-defense law provides a framework for analyzing tangible
failure scenarios that can inform the design of robots and their algorithms.
Studying self-defense is particularly important for ground robots since they
operate within public environments, where they can pose a legitimate threat to
the safety of nearby humans. Moreover, even if ground robots can guarantee
human safety, the perception of a physical threat is sufficient to justify
human self-defense against robots. In this paper, we synthesize works in law,
engineering, and social science to present four actionable recommendations for
how the robotics community can craft robots to mitigate the likelihood of
self-defense situations arising. We establish how current U.S. self-defense law
can justify a human protecting themselves against a robot, discuss the current
literature on human attitudes toward robots, and analyze methods that have been
produced to allow robots to operate close to humans. Finally, we present
hypothetical scenarios that underscore how current robot navigation methods can
fail to sufficiently consider self-defense concerns and the need for the
recommendations to guide improvements in the field.
