When is it suitable to use observation in requirements elicitation?

Observation is suitable in requirements elicitation when the context of use is complex or not easily articulated by users, such as in environments where users may not be fully aware of their own needs. It is also effective when gathering data on user interactions with existing systems or processes, allowing for insights into behaviors and workflows that may not be captured through interviews or surveys. Additionally, observation can help identify unmet needs or pain points that users may not explicitly express.