What is the term used for an individual that raises concerns about suspicious activities?

The term "suspicious person" is used to describe an individual who raises concerns about suspicious activities. This designation is often employed in law enforcement and security contexts to identify someone whose behavior or presence may be unusual or cause concern among the public or authorities. The terminology implies that there may be a reason to be wary of the person's actions without necessarily accusing them of any wrongdoing. This category encompasses a wide range of situations where someone might be observed acting in a way that prompts questions or reports, allowing law enforcement to investigate further.

In contrast, the other terms do not convey the same level of concern or specificity regarding the behavior that led to the reporting. "Suspicious subject" could imply a broader category without the human element that 'person' provides. "Potential suspect" implies that an individual is considered involved in potential criminal activity, which is a more definitive accusation and does not cover individuals who are reported merely for being suspicious without evidence of guilt. "Unknown character" lacks the precise context applied in law enforcement and does not specifically refer to someone raising concerns about activities.