What does accumulated degree hours (ADH/ADD) measure and how is it used in PMI estimation?

What does accumulated degree hours (ADH/ADD) measure and how is it used in PMI estimation?

• A. ADH/ADD sums heat units required for insect development; used to estimate PMI
• B. A measure of insect size at death
• C. A method for DNA extraction
• D. A type of forensic imaging modality

Answer: (A)

Accumulated degree hours and accumulated degree days quantify the heat needed for insect development. Because insects develop only when temperatures exceed a lower developmental threshold, we add up the temperature excess above that threshold over time. The total heat units accumulated until the insect reaches a given developmental stage links to how long it has been since death. By comparing the observed developmental stage of the insect to species-specific heat-unit requirements, we estimate the postmortem interval. For example, if a species needs a certain number of ADD to reach a particular larval stage and daily mean temperatures provide a consistent heat excess, you can divide the required heat by the daily heat gain to approximate the time since death. Temperature fluctuations and microclimates can affect the estimate, as can species differences, so ADD/ADH must be applied with species-specific data. This concept is not about insect size, DNA extraction, or imaging modalities, which is why those options don’t fit.

Accumulated degree hours and accumulated degree days quantify the heat needed for insect development. Because insects develop only when temperatures exceed a lower developmental threshold, we add up the temperature excess above that threshold over time. The total heat units accumulated until the insect reaches a given developmental stage links to how long it has been since death. By comparing the observed developmental stage of the insect to species-specific heat-unit requirements, we estimate the postmortem interval.

For example, if a species needs a certain number of ADD to reach a particular larval stage and daily mean temperatures provide a consistent heat excess, you can divide the required heat by the daily heat gain to approximate the time since death. Temperature fluctuations and microclimates can affect the estimate, as can species differences, so ADD/ADH must be applied with species-specific data.

This concept is not about insect size, DNA extraction, or imaging modalities, which is why those options don’t fit.