Understanding Undetermined

An Article from the Perspective of a Fire Investigator - Vithyaa Thavapalan

Fire investigations are inherently detailed processes. Despite scene examinations, witness interviews, laboratory analyses and examinations and the application of the scientific method, there are times when the cause of a fire cannot be definitively established. In these situations, investigators must classify the fire cause as “undetermined.”

The Role of the Scientific Method

NFPA 921 (2024) emphasises using the scientific method as the foundation for fire investigations. We investigators gather data, formulate hypotheses, test those hypotheses, and then draw conclusions (see NFPA 921 2024, Chapter 4, “Basic Methodology”). If the available evidence does not definitively support a single hypothesis, or if multiple hypotheses remain equally plausible, the result must be that the cause of the fire is “undetermined.”

Insufficient or Destroyed Evidence

One of the most common reasons for an undetermined classification is insufficient evidence. Fire scenes are often heavily damaged, and key indicators such as burn patterns, ignition devices, or electronic data may be destroyed by intense heat or firefighting efforts.

Even with advanced technology like 3D laser scanning and specialised forensic analyses, some evidence may be too damaged or completely missing, preventing a conclusive determination.

Multiple Possible Causes

When more than one ignition source or scenario is plausible, and the available evidence does not eliminate one cause over another, NFPA 921 (2024) advises that investigators may have to classify the fire as undetermined (see NFPA 921 2024, Chapter 19, Cause Determination). For example, if an electrical malfunction or unattended cooking could have caused a kitchen fire, and there is insufficient evidence to distinguish one from the other, the correct conclusion may be “undetermined.”

Importance of a Thorough Investigation

An undetermined classification does not mean the investigation was incomplete or improperly conducted. Instead, it often reflects the professional integrity of the investigator in adhering to NFPA 921’s guidelines. When investigators classify a fire cause as undetermined, they are acknowledging that:

1. They have considered all available evidence.

2. They have applied the scientific method.

3. They have ruled out or confirmed various hypotheses to the extent allowed by the evidence.

4. No single hypothesis can be conclusively proven or disproven.

   
   

This transparency is crucial for maintaining the credibility of the investigative process. If new evidence or technology emerges later, NFPA 921 (2024) indicates that an undetermined classification can be revisited, and investigators may reopen the case to reach a more definitive conclusion (see NFPA 921 2024, Section 19.8, Reclassification of Fire Cause).

Fires are destructive events. Despite the guidelines of NFPA 921 (2024), some investigations will inevitably end in an undetermined classification. When evidence is insufficient or conflicting, or when multiple causes remain equally likely, it is both proper and necessary for fire investigators to classify the cause as “undetermined.” This impartial and scientific approach highlights the professionalism required in fire investigation, ensuring that conclusions are based on facts and not on speculation.

Ultimately, undetermined does not signify failure—it reflects an honest and science-evidence based assessment of the available information. By following NFPA 921’s methodology and ethical standards, fire investigators maintain the integrity of the investigative process and uphold the pursuit of truth within the fire and emergency services community.

References

• National Fire Protection Association. (2024). NFPA 921: Guide for Fire and Explosion Investigations. Quincy, MA: NFPA.

• NFPA 921 (2024), Chapter 4, “Basic Methodology”

• NFPA 921 (2024), Chapter 14, “Investigator Interviewing Techniques”

• NFPA 921 (2024), Chapter 16, “Documentation of the Fire Scene”

• NFPA 921 (2024), Chapter 17, “Physical Evidence”

• NFPA 921 (2024), Chapter 19, “Cause Determination”