DATA-FUSION MODEL FOR FORENSIC IDENTIFICATION OF 

ILLICIT CHEMICALS

Ashot Nazarian (NIST) and Cary Presser (NIST)

Objectives

 Statistically combining heterogeneous forensic data, 

including both sample signatures and analyzed collected 

evidence, can enhance the overall confidence level of 

identifying the composition of improvised and precursor 

chemicals. Figure 1 presents an approach for combining 

heterogeneous forensic data, i.e., collected data, chemical- signature measurements, commercial sources for precursors 

and additives/additional chemicals, and process information.

 The presence of precursors (i.e., everyday household 

chemicals) with a significant number of additives, act as 

“confusers” that make existing reference data (mostly for 

pure chemicals) unusable (Fig. 2). This results in limiting 

detection accuracy (often to below 50 %), making the 

evidence inadmissible in court. Our innovation is based on a 

novel data-fusion model approach (currently using Bayesian 

networks) that combines all relevant heterogeneous data in a 

way that transforms “confusers” into “markers” and 

increases detection accuracy and confidence beyond 95 %. 

Scenario

 Consider TATP (triacetone triperoxide), which is the most commonly used improvised 

explosive material; i.e., recent terrorist events in the UK (Oct. 22), NY (Sept. 18), 

NJ (Sep. 17), France (Jul. 14), Belgium (Mar. 22). 

 Suppose that after collecting and analyzing samples, forensic teams discover that the 

certainty of identifying the explosive material is in question due to the presence of 

“confusers” (other secondary chemical compounds) in measured signatures. 

 To address this issue, our data fusion model will use reference processes, data, and 

analytical signatures, along with on-site observables and collected signatures to better 

infer the identity of the improvised substance. 

 For example, TATP is synthesized by mixing acetone, hydrogen peroxide, and an acid 

(e.g., sulfuric acid) that serves as a catalyst. One of commercial sources for acetone is a 

nail polish remover which may include acetone, ethyl acetate, and isopropyl alcohol. 

Similarly, hydrogen peroxide is commercially available in wood bleach products that also 

contain a number of other ingredients. Thus, measured signatures of the trace substance 

is likely to contain numerous features attributed to the TATP, sulfuric acid, and others 

ancillary substances. 

 To better understand the challenge for conventional forensic analysis, criminals and 

terrorists have available a variety of commercial sources for acetone (with additional 

additives), hydrogen peroxide, and different acids, which can result in many different 

possible outcomes. Criminals and terrorist are adaptive and evolve by using different 

alternatives.

 However, our system captures these various possibilities (‘limitations’) and vulnerabilities 

though statistical data-fusion metrics that account for: (a) materials/ingredients 

availability (at specific locations), (b) cost, (c) process complexity, (d) special skills 

requirements, (e) special equipment, attributions, and safety needs.

Site collected data + additional available data + signatures = heterogeneous data fusion

Collaborators in the NIST Statistical Engineering Division

• Blaza Toman (Data statistical analysis)

• Simone Gittelson (Bayesian Networks)

National Institute of Standards and Technology

U.S. Department of Commerce

Figure 1

Common effect probabilistic relationships

TATP (composed of Acetone, 

Hydrogen Peroxide, and Acid)

TATP

Commercial product: Degreaser-Acetone (notional)

MASS SPECTRUM

Marker:

C4H8O2

Marker:

C3H8O

Marker: 

H2SO4

TATP Reference Signature

TATP Actual Signature 

Degreaser Glue

Remover

Paint

Thinner

Acetone

Nail Polish

Remover

Disinfectant

Wood

Bleacher

Hair

Bleacher

Rocket

Propellant

Hydrogen

Peroxide

Sulfuric

Acid

Hydrochloric

Acid

Citric

Acid

Nitric

Acid

Acetic

Acid

Phosphoric

Acid

Catalyst

(Acid)

Relative Intensity Relative Intensity

Figure 2