What does an absence of CO2 in the bloodstream at a fire scene suggest?

The absence of CO2 in the bloodstream at a fire scene suggests that the person was dead prior to the fire. Carbon dioxide (CO2) is a waste product produced by the body's metabolism, and its levels in the bloodstream indicate respiratory function and oxygenation. If CO2 is absent, it likely means that the individual was not breathing and therefore not metabolizing oxygen or producing CO2 at the time of the fire.

In fire scenarios, exposure to smoke and other toxic gases typically results in the inhalation of those products, leading to the accumulation of CO2 if a person was alive during the event. Therefore, the absence of CO2 would not support the idea that the person was alive, nor would it indicate physical trauma solely caused by the fire. This absence serves as a key indicator for investigators to understand that the individual may have already been deceased before the fire started.