Thermal Bias
Definition
Systematic under- or over-estimation of developmental temperature caused by using distant weather-station data, solar radiation on an exposed body, or micro-environmental features of the specific location. Each bias shifts the PMI estimate in a predictable direction.
- Cause examples
- Distant weather station, sun exposure, microhabitat
- Effect
- Systematic PMI over- or under-estimate
- Direction
- Predictable per bias type
- Field
- Entomological PMI estimation
Common questions
Which direction does solar exposure push the PMI estimate?+
A body in direct sun runs warmer than nearby weather-station readings suggest, so using station data underestimates the true accumulated degree days, inflating the calculated PMI and pushing the estimated time of death earlier than it truly was.
How is thermal bias corrected in casework?+
Investigators place a data logger at the scene for a period after discovery to record local conditions, or apply a documented offset derived from regression models comparing station and scene temperatures.
Related terms
- Accumulated Degree Hours (ADH)
- A temperature-corrected measure of developmental time. Calculated by summing (hourly ambient temperature minus the species-specific base temperature threshold) across the period of...
- Colonisation Interval
- The elapsed time since the first insect colonised the body. Often shorter than the PMI if access was delayed by concealment. An...
- Entomotoxicology
- The analysis of insect tissue for drugs and toxins when decomposition has made conventional biological fluids unavailable. Blow-fly larvae feeding on a...
- Maggot-Mass Thermogenesis
- The elevation of temperature within a dense larval aggregation by the combined metabolic heat of thousands of larvae. Documented elevations range from...
- Minimum PMI (PMImin)
- The shortest interval consistent with the entomological evidence. In practice this is what entomologists estimate: a floor on elapsed time based on...