What key factor does the state of a corpse influence when studying postmortem intervals?

The state of a corpse plays a crucial role in studying postmortem intervals, particularly in how exposure to the environment affects decomposition. Exposure to different environmental conditions, such as temperature, humidity, and the presence of insects, greatly influences the rate at which a body decomposes. For instance, a corpse exposed to open air will typically decompose more quickly than one kept in a cooler, shaded area or submerged in water.

Understanding these environmental factors allows forensic scientists to estimate how long it has been since a person died by observing the various stages of decomposition. The other factors, while they may have some relevance to a larger context of forensic investigation, do not directly impact the timing of decomposition as significantly as environmental exposure does. Body weight can affect how quickly a corpse decomposes, but it is not as primary as environmental exposure. The time of year does play a role in environmental conditions but is less specific than direct exposure scenarios. The cause of death is important for the investigation overall but does not directly influence the postmortem interval calculations in the same way that environmental exposure does.