Military Defense Investigation Knowledge Base
Military Defense Investigation Authority Publication
Authority Publication No. DI-138
Comparing Line-of-Duty, Safety, Mishap, and Criminal Investigations of the Same Event
Independent Military Defense Investigations
Supporting Attorneys, Service Members, and Families
Publication Date: August 24, 2026
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Executive Summary
Comparing military mishap, safety, line-of-duty, and criminal investigations requires the defense to distinguish each inquiry's purpose, evidence, scope, restrictions, assumptions, and findings before relying on its conclusions.
A single military event may generate multiple investigative records. Line-of-duty, safety, mishap, and criminal investigations can examine overlapping facts while serving different purposes and relying on different evidence, terminology, assumptions, privileges, and analytical methods.
DI-138 explains how defense investigators can identify the appointment and authority for each inquiry, inventory scene evidence and witness statements, separate factual from analytical material, recognize privilege or use restrictions, and compare timelines, assumptions, terminology, and conclusions.
The publication's practical example involves a mishap report and a criminal report reaching different conclusions because they use different data and serve different purposes. A comparison matrix identifies shared facts, unique evidence, and assumptions rather than treating either report as automatically controlling.
The purpose is to reconstruct the source and decision sequence behind each investigation so counsel can understand why the reports agree, disagree, or leave important questions unresolved.
DI-138 explains how military defense investigators compare line-of-duty, safety, mishap, and criminal investigations by identifying each inquiry's purpose, authority, evidence, restrictions, assumptions, shared facts, and unique conclusions.
Who Should Read This Publication?
Military Defense Counsel
Use the comparison of investigative authority, evidence, restrictions, assumptions, and findings to determine what materials require discovery, expert review, formal process, or further investigation.
Defense Investigators
Map every inquiry separately, preserve original evidence, identify the source of repeated statements, compare timelines and terminology, and build a matrix showing shared facts, unique evidence, and unresolved conflicts.
Service Members
Understand why two official investigations of the same event may reach different conclusions and why the underlying evidence and purpose of each inquiry matter more than the report title alone.
Qualified Experts or Specialists
Review complete underlying materials and clearly defined questions, recognizing that safety or mishap analysis and criminal investigative analysis may use different data, assumptions, and purposes.
Families
Understand that apparently conflicting official reports do not necessarily mean one is false; the defense team must identify what evidence each investigation actually used and what each process was designed to determine.
Companion Video
This companion video expands on the investigative concepts presented in this Authority Publication through additional explanation, practical examples, and professional investigative insight.
About Michael West
The investigative guidance presented throughout these Authority Publications is based upon decades of professional experience conducting military, federal, criminal, civil, and private investigations. The principles discussed in these publications are drawn from real investigative work involving complex cases, witness development, evidence analysis, and factual case preparation.
Michael West has served as a Special Agent with the United States Air Force Office of Special Investigations (AFOSI) and the Department of Defense Inspector General, conducted federal background investigations, and spent decades working as a licensed private investigator supporting attorneys, businesses, service members, and private clients. Throughout his career, his work has focused on identifying facts, locating witnesses, analyzing evidence, and strengthening the factual foundation of legal cases through independent investigation.
The Military Defense Investigation Knowledge Base was created to share that investigative experience in a practical, understandable format. Its purpose is to help attorneys, service members, and families better understand the investigative process, ask more informed questions, and recognize opportunities where independent investigation may strengthen the defense.
Important Information
This Authority Publication is provided for educational and informational purposes and is intended to help readers better understand military defense investigations and the investigative process. It is based upon professional investigative experience and is designed to provide practical investigative insight rather than legal advice.
Every military case is unique. The investigative strategies, factual issues, and legal considerations applicable to one case may not apply to another. Readers should consult with a qualified attorney regarding legal rights, legal strategy, and decisions involving their individual circumstances.
Nothing contained in this publication should be interpreted as creating an attorney-client relationship or an investigator-client relationship. References to investigative techniques, procedures, or case examples are provided solely to illustrate investigative principles and should not be considered legal guidance.
Effective military defense is strengthened by informed legal representation supported by thorough factual investigation. The purpose of these Authority Publications is to help readers better understand that investigative process so they can communicate more effectively with qualified legal counsel and make informed decisions throughout the military justice process.