Which of the following types of investigations occurs when arson investigation experts are called to assist with gathering and processing evidence?

The correct choice is related to the specific context of hiring specialized experts in the field of arson. When arson investigation experts are brought in, it signifies that the nature of the incident is not just a typical fire or accident but involves circumstances that raise suspicion about the cause. This kind of investigation focuses on determining if foul play was involved, which aligns more with a specific type of inquiry into suspicious activities surrounding the fire incident.

In a standard routine investigation, responders may handle typical incidents without the need for specialized knowledge about fire dynamics or arson techniques. A criminal investigation broadly encompasses various crimes and does not specifically pinpoint the nuances related to fire origin and purpose, which are crucial in arson cases. While arson investigation is a precise term that directly describes the field, it does not capture the broader context of the gathering and processing of evidence in a case considered suspicious, where expert assistance is often needed. This highlights the unique nature of investigations centered around suspicious fires, effectively clarifying why that choice best fits the scenario described.