G13 gives the benefit of the doubt to the "offensive" robot. In games such as Spin-Up in which a common game element can score points for either alliance and whose state is contented over the course of the match, referees often run into situations where the line between "offense" and "defense" is blurred.
For example, in Spin-Up we have the rollers that can score for either Red or Blue (or neither). If a roller's current state shows Blue, is a Red robot that heads towards it with the (obvious) intent to change it (emphasis added) first to unscored state, and then to Red an "offensive" or "defensive" action? The argument for this being a "defensive" action is that the necessary sequence of events to "gain" points for Red is to first descore points for Blue. Is the act of descoring "offensive" or "defensive"?
If the answer above is that the Red robot is acting "defensively" when it descores an element, what then to make of a Blue robot that is preventing Red from descoring their roller? Is the Blue robot acting "defensively" up to the point where the roller becomes descored? Common sense would seem to dictate that a robot seeking to preserve current game-state is acting "defensively". But now we are left with 2 opposing robots potentially acting "defensively", giving neither the benefit of the doubt (which, fair enough). Does the Blue robot then become "offensive" (and, indeed too, the Red robot) when the roller is in a state that scores for neither team? Now we have 2 opposing robots both acting "offensively" and thus potentially giving both the benefit of the doubt.
If the answer that "descoring" is "offensive", then what to make of robots carrying/pushing discs in the opposing low-goal? Suppose a Blue robot (where Blue is carrying 1-3 discs) is in the Red low-goal. Since the disc carried by the Blue robot would currently score for Red, is Blue acting "offensively" when trying to exit the low-goal? Is Red acting "offensively" when it then pushes Blue back into the Red low-goal? What if Blue was trying to shoot when Red pushed Blue in? Are both robots in that moment "offensive"? Does Red "instantly" transition from "offensive" to "defensive" the moment the discs Blue carries fully enter the Red low-goal?
In summary, referees frequently encounter situations where opposing robots interacting with each-other do so in ways in which interactions between 2 opposing robots are not easy to identify (or explain post-match) which robot is "offensive" or "defensive".