Which term describes something that is capable of causing death?

The term that describes something capable of causing death is "lethal." This word is derived from the concept of causing death or being fatal, and it often pertains to substances, actions, or situations that can lead to a fatal outcome. In the context of law enforcement, understanding what is lethal can be crucial for making informed decisions about safety and the potential risks involved in various scenarios.

The other terms in the question offer contrasting meanings. "Harmless" refers to something that does not cause injury or damage, while "innocuous" indicates something that is not harmful or offensive. "Beneficial" describes something that produces good effects or advantages. Therefore, these terms collectively signify concepts that do not align with the idea of causing death, highlighting why "lethal" is the appropriate choice in this context.