Dear Mr. Hicklin,
Thank you for posting your question on History Hub.
For records related directly to Mr. Skubinna you will want to contact the Bundesarchiv. They will have custody of personnel records or any surviving records that may have been created during World War II by the German government.
The Collection of Foreign Records Seized - Captured German Records may also be of interest to your research. Based on what you know about the work he did Mr. Skubinna did during the war and his associations, you may be able to identify series of interest. The Captured German records in our custody are microfilm copies and the originals were returned to Germany and are in the custody of the Bundesarchiv. For information regarding these records please visit https://www.archives.gov/research/captured-german-records/foreign-records-seized.html.
Unfortunately at this time we have been unable to identify files for Mr. Skubinna specifically. His name is not among those listed in Records of the Army Staff (Record Group 319) Entry 134 - Investigative Records Repository (IRR) Personal Name Files. He is also not listed in the European Name Index to War Crimes Case Files in Entry 142 - Records of the Office of the Judge Advocate General (Army) (Record Group 153).
We recommend contacting the National Archives at College Park Reference Branch for a deeper search into their records for the testimony Mr. Skubinna provided against the SS. The email for that office is firstname.lastname@example.org.
We hope this information is helpful in beginning your research.
The National Archives and Records Administration