STATISTICS TASK GROUP:

NEVER HAVING TO SAY YOU’RE 

CERTAIN
Karen Kafadar, Chair, STG

Chair & Commonwealth Professor

Dept of Statistics, Univ of Virginia

kkafadar@virginia.edu

David Banks, Duke: Vice-Chair

William Guthrie, NIST: Executive Secretary
STG Mission

■ Provide advice to OSAC units on proper use & explanation of 

statistical concepts used in standards posted on OSAC 

registry

■ Serve as members on OSAC units to ensure practical advice 

relevant to units’ disciplines

■ Ensure consistent statistical advice across OSAC units

■ Collaborate with forensic practitioners to develop proper, 

validated, and practical statistical procedures

■ Provide other statistical advice as requested

■ Serve as advisers, not as intruders
STG: OSAC statisticians & 

affiliates

■ Karen Kafadar (UVA), FSSB

■ SAC Statisticians:

– Biology: Bruce Wier (UW), Simone Gittelson (University of 

Technology - Sydney)

– Chemistry: William Guthrie (NIST)

– Crime Scene: Jerry McGwin (UAB)

– Digital/IT: Abhyuday Mandal (U-GA)

– Physics/Pattern: Hal Stern (UCI)
SAC/Subcommittee 

Statisticians:

(15 of 25 SubSACs have statisticians)

■ Chemistry: Will Guthrie, NIST

– Gunshot Residue: Cliff Spiegelman, Texas A&M

– Materials/Trace Evidence: Cédric Neumann, South 

Dakota State Univ

– Geological Materials: Martin Wells, Cornell

■ Crime Scene:

– Fire & Explosion: Mark Johnson, Univ of Central Florida

– Medico/Legal Death Investigation: Gerald McGwin, Univ

AL
■ Physics/Pattern Evidence: Hal Stern, UC-Irvine

– Blood Stain: Haonan Wang, Colorado State Univ

– Footwear & Tire: Steven Lund, NIST

– Firearms & Toolmarks: Max Morris, Iowa State Univ

– Questioned Documents: Chris Saunders, South Dakota State 

Univ; Mark Lancaster, Northern Kentucky Univ

■ Others: David Kaye, PSU (LRC), Bill Thompson, UCI (HFC), 

Alicia Carriquiry, ISU
Statistics: Raison d’être

■ Help to define the problem (J.W. Tukey: “Often 

finding the question is harder than finding the solution”)

■ Draw valid inferences from data

■ Understand how the process can be “measured”

■ Identify sources of variability: what influences might affect the 

data? (materials, methods, personnel, ...)

■ Help to assign quantitative measures to qualitative outcomes

■ Work with forensic scientists to understand, characterize, and 

quantify sources of uncertainty in the process

■ Design studies to understand sources of variability in the 

forensic process; factors that influence the targets 

(measurements, configurations, etc.) & quantify their effects
Work Products

■ Comments on proposed Standards, including seized drugs 

(E2548-11) and glass standards (E2926-13: XRF; 

E2330-12: ICP-MS; E2927-16: LA-ICP-MS)

■ Participate in other Task Groups (e.g., Conclusions Task 

Group; Interpretations for testimony)

■ Confer on best practical guidance

■ Many STG members participate widely in forensic statistics 

(CSAFE, SAMSI, journal referee, etc.)
Submitting inquiries

■ Send to unit statistician (most knowledgeable about the 

area); suggest you copy the statistician at next level (e.g., 

subcommittee and SAC)

■ Please do not hesitate to send reminders. We are used to 

being referees for journal article submissions

■ For faster response, please direct reviewer to specific 

section(s) of most (statistical) concern
kkafadar@virginia.edu

QUESTIONS?