A relative deserted his Union infantry unit in the US Civil War. He petitioned his desertion charge approximately fifteen years later and his petition was denied. In reviewing adjutant general records, I discovered that there were three other men who were listed as deserting on the same day as my relative.
So I requested the compiled military service records of these fellow deserters of my relative in addition to any information that may have been in their record regarding an appeal of the desertion charge–just in case there was a mention of the group as a whole.
Another relative was involved in a crime on the Mississippi River in the 1780s. Several of his compatriots were named as well. Further research on them indicated one was his brother-in-law and that they were all from the same county in the Carolinas.
Any associate of an ancestor is an associate who should be researched whether their group activities were legal or not.