Army Techniques Publication (ATP) 3-39.12 is aligned with Field Manual (FM) 3-39, the Military Police Corps Regiment's operational doctrine, and Army Tactics, Techniques, and Procedures (ATTP) 3-39.10. It is intended as a guide and toolkit for military police investigators, USACIDC special agents (SAs), and military police Soldiers conducting law enforcement (LE) and LE investigations. It also serves to educate military police commanders and staff on LE investigations capabilities, enabling a more thorough understanding of those capabilities. This increased understanding facilitates staff planning, resource allocation, and the ability to articulate LE investigative capabilities and requirements to supported commanders and organizations.The principal audience for ATP 3-39.12 is Army military police personnel, which include Department of the Army (DA) civilian police, conducting LE investigation activities while assigned to military police brigades, battalions, companies, detachments, United States (U.S.) Army Criminal Investigation Command (USACIDC) elements, military police platoons supporting brigade combat teams, and Provost Marshal (PM) staffs. The manual also provides military police commanders and staffs with a framework and understanding of LE investigations and investigative capabilities that support decisive action.Commanders, staffs, and subordinates ensure their decisions and actions comply with applicable U.S., international, and, in some cases, host-nation (HN) laws and regulations. Commanders at all levels ensure their Soldiers operate in accordance with the law of war and the rules of engagement (see FM 27-10).ATP 3-39.12 uses joint terms where applicable. Selected joint and Army terms and definitions appear in both the glossary and the text. Terms for which ATP 3-39.12 is the proponent manual (the authority) are marked with an asterisk (*) in the glossary. Definitions for which ATP 3-39.12 is the proponent publication are boldfaced in the text. For other definitions shown in the text, the term is italicized and the number of the proponent publication follows the definition.ATP 3-39.12 applies to the Active Army, Army National Guard (ARNG)/Army National Guard of the United States (ARNGUS), and United States Army Reserve (USAR) unless otherwise stated.The proponent of ATP 3-39.12 is the U.S. Army Military Police School (USAMPS).Chapter 1 LAW ENFORCEMENT INVESTIGATION CAPABILITIES AND SUPPORTChapter 2 PHYSICAL EVIDENCEChapter 3 INTERVIEWS AND LAW ENFORCEMENT INTERROGATIONSChapter 4 CRIME SCENE PROCESSING AND DOCUMENTATIONChapter 5 PHYSICAL SURVEILLANCEChapter 6 UNDERCOVER MISSIONSChapter 7 DEATH INVESTIGATIONSChapter 8 ASSAULT AND ROBBERY INVESTIGATIONSChapter 9 SEX CRIME INVESTIGATIONSChapter 10 CRIMES AGAINST PROPERTY INVESTIGATIONSChapter 11 FRAUD AND ECONOMIC CRIME INVESTIGATIONSChapter 12 DRUG CRIME INVESTIGATIONSChapter 13 COLLISION (TRAFFIC ACCIDENT) INVESTIGATIONSAppendix A INVESTIGATIONS SUPPORT IN AN OPERATIONAL ENVIRONMENT Appendix B ELECTRONIC DEVICES Appendix C FORENSIC EXPERIENTIAL TRAUMA INTERVIEW Appendix D FORMS Appendix E SOURCES Appendix F INVESTIGATIONS CHECKLISTS Appendix G COMMONLY ABUSED DRUGS Appendix H ENVIRONMENTAL CRIMES Appendix I INVESTIGATOR TESTIMONYAppendix J COLLISION DIAGRAMMING Appendix K COLLISION CALCULATIONSGLOSSARY REFERENCES