Scientific Method
Definition
As applied in NFPA 921: the six-phase process of recognising the need, defining the problem, collecting data, analysing data, developing and testing hypotheses, and selecting the final hypothesis that best fits the evidence.
- Governing standard
- NFPA 921, Guide for Fire and Explosion Investigations
- Phase count
- Six phases
- Core sequence
- Recognize need, define problem, collect and analyze data, test hypotheses
- Final step
- Select the hypothesis that best fits all available evidence
- Applies to
- Origin and cause determination in fire investigation
Common questions
Why does fire investigation formally adopt the scientific method instead of an investigator's experience alone?+
Courts in the United States require origin and cause opinions to meet reliability standards such as Daubert, and an undocumented hunch does not survive cross-examination. Applying a documented, repeatable process lets an expert show how a conclusion was reached, not just what it was.
What is the difference between a working hypothesis and the final hypothesis in this process?+
A working hypothesis is any candidate explanation for the fire's origin and cause that has not yet been tested against the physical evidence. The final hypothesis is the one that survives testing against every other candidate and against evidence that could disprove it, which NFPA 921 calls negative corpus if done improperly.
Can an investigator skip straight to data collection without defining the problem first?+
Skipping the problem-definition phase risks collecting the wrong data or missing evidence that later proves relevant. NFPA 921 treats the phases as sequential precisely because each one narrows and directs the next.
Related terms
- 360-Degree Imaging
- Panoramic imaging systems (Matterport, Leica RTC360, FARO Focus) producing navigable point clouds and photospheres of fire scenes, enabling retrospective measurement and remote...
- ABE Guidance
- Achieving Best Evidence in Criminal Proceedings, the UK guidance framework published by the Ministry of Justice governing how investigators should conduct interviews...
- ASTM E1618
- Standard Test Method for Ignitable Liquid Residues in Extracts from Fire Debris Samples by Gas Chromatography-Mass Spectrometry. The active analytical standard defining...
- Confirmation Bias
- The cognitive tendency to search for, interpret, favour, and recall information in a way that confirms or supports one's prior beliefs or...
- Daubert Standard
- The US federal evidentiary standard (Daubert v. Merrell Dow Pharmaceuticals, 1993) requiring that expert testimony be based on scientifically valid methods with...
- Layered Excavation
- The systematic removal of fire debris in documented layers, from the surface downward and from low-damage to high-damage areas, to preserve the...
- Negative Corpus
- The discredited practice of concluding incendiary fire cause by eliminating all identifiable accidental causes without positive physical evidence of intentional fire-setting. NFPA...
- NFPA 921
- US National Fire Protection Association Guide for Fire and Explosion Investigations. The internationally accepted methodology Indian fire investigators and SFSL fire divisions...
- Total Station
- An electronic instrument that simultaneously measures horizontal and vertical angles and distance to a reflective prism, computing three-dimensional coordinates directly. Typical angular...