The history of Russian-American relations is full of various dramatic moments. There were periods of strategic partnership and alliance, but also those of aggravation of diplomatic and trade relations during the so-called Cold War. One thing persists from the moment the United States was formed in the 18th century to early 21st century: Russia and the United States have been allies in all military conflicts or maintained mutual neutrality. At the same time, as history shows, among political and bureaucratic elites of the United States, there have always been opponents of Russia as a geopolitical entity who provided direct assistance to its military opponents. One of these episodes occurred in 1915, when Moser, the American consul in the city of Harbin located on the territory of the Chinese Eastern Railway — a highway that ran along Manchuria and connected Chita with Vladivostok — found himself an object of cultivation of the Irkutsk Gubernia Gendarmerie Directorate. The article introduces into scientific use a document which permits to assess the degree of involvement of the American diplomat in the release of German prisoners of war, which caused a diplomatic demarche of Russia, expulsion of the consul, and, accordingly, a diplomatic scandal in Russian-American relations in 1915. This document is court opinion of November 6, 1915 of the investigator for especially important cases of the Irkutsk District Court M.S. Strazov based on secret survey of the captain of a separate corps of border guards, assistant to the head of the department at the gendarmerie-police directorate of the Chinese Eastern Railway A. M. Bokastov who had carried out the surveyance; on protocol of interrogation of non-commissioned officer Karl Schultz who fled the Russian camp in Western Siberia (in the city of Tara, Tobolsk gubernia) and was supported by the American diplomat; and on protocol of interrogation of J. E. Mandelstam accused of organizing this escape. Through the agency of their employees insinuated in groups of German officers who fled from the Russian camps in Siberia to China territories, the heads of gendarmerie directorate learned that the American diplomat not only supplied prisoners of war with money for escape, but also recommended them to makers of falsified documents and guides transporting runaways. Cultivation undertaken in 1915 by the Irkutsk Gubernia Gendarmerie Directorate resulted in arrest of Russian subjects of German and Jewish origin who, for various reasons, participated in organization of escapes of German and Austro-Hungarian prisoners of war from concentration camps located in Siberia and in the Far East.