Please read that post at this link
This illustration is from Harper's Weekly of October 18, 1862 and is captioned: "The Assassination of General Nelson by General Jefferson C. Davis - sketched by Mr. H. Mosler" It is courtesy of www.sonofthesouth.net I thought it was appropriate to use it in this discussion, but with my first post already being so long, I added it to this entry instead.
Listed below are the theories I found and the sources in which I found them. These sources either cited a specific reason for Davis to go unpunished or included enough reaction to the event that I found it appropriate to include these reactions as possible explanations about how this event played out.
My breakdown of the categories and how often I saw them was (a couple of sources used more than one that fit into the categories I decided to use)
1. Davis's influential friends or individuals helping him: 7 times (5 times Oliver Morton, 2 times Horatio Wright)
2. Nelson's reputation/unpopularity: 5 times (plus 1 other disagreeing with this view)
3. "Matter of honor:" 3 times
4. Buell's command uncertainty/business: 4 times
5. Union need for talent and leadership in the theater: 3 times
6. Davis was honorably acquitted at trial: 1 time. (His obituary mentioned this, but this claim is incorrect. I still feel it is worth mentioning)
Bobrick, Benson. Testament: A Soldier's Story of the Civil War, New York, Simon & Schuster,
Engle, Stephen Douglas. Don Carlos Buell: Most Promising of All, Chapel Hill, NC, University of North Carolina Press, 1999. Print.
Heidler, David S., ed and Heidler, Jeanne T., ed. Encyclopedia of the American Civil War: A Political, Social and Military History, New York, W.W Norton & Company, 2000. Print.
Noe, Kenneth W. Perryville: This Grand Havoc of Battle, Lexington, KY, University Press of Kentucky,
Street Jr, James, and Editors of Time-Life Books. The Struggle for Tennessee: Tupelo to Stones River, Alexandria, VA, Time-Life Books, 2nd printing, revised 1987. Print.
Powell, David A "Women and War, Politics and Bedfellows." Retrieved October 23, 2010 from http://chickamaugablog.wordpress.com/
Talbott, Tim, "Personality Spotlight: William "Bull" Nelson." Retrieved October 23, 2010 from http://randomthoughtsonhistory.blogspot.com/
Clark, Donald A. "General Jefferson Columbus Davis, USA" Historycentral.com Accessed October 23, 2010, http://www.historycentral.com/bio/UGENS/USADavis.html
Clark, Donald A. "General Nelson William Bull USA" Historycentral.com, Accessed October 23, 2010, http://www.historycentral.com/bio/UGENS/USANelson.html
Groom, Winston, "Murder in the Civil War" historynet.com, Accessed October 23, 2010, http://www.historynet.com/murder-in-the-civil-war.htm/1
Robinson, Bill, "Battlefield Park getting pistol belonging to Gen. Nelson's killer" RichmondRegister.com, Accessed October 23, 2010, http://richmondregister.com/localnews/x752937183/Battlefield-Park-getting-pistol-belonging-to-Gen-Nelson-s-killer
Author unknown, "Jefferson C. Davis" worldlingo.com, Accessed October 23,2010, http://www.worldlingo.com/ma/enwiki/en/Jefferson_C._Davis#Murder_of_General_Nelson
Author unknown, "Although not convicted of murder, Davis was passed over for advancement in rank" KentuckyCivilWarBugle.com, Accessed October 23, 2010, http://www.thekentuckycivilwarbugle.com/2010-1Qpages/murder.html
Author unknown, "Gen. Jefferson C. Davis Dead" query.nytimes.com, Accessed October 23, 2010, http://query.nytimes.com/mem/archive-free/pdf?res=F60E11FC3D5A137B93C0A91789D95F4D8784F9
Author unknown "An encounter between Union generals turns fatal" history.com, Accessed October 23, 2010, http://www.history.com/this-day-in-history/an-encounter-between-union-generals-turns-fatal
Author unknown "Camp Nelson National Cemetery" United States Department of Veterans' Affairs website. Accessed October 23, 2010, http://www.cem.va.gov/pdf/cnelson.pdf (direct link to the article in .pdf format) or http://www.cem.va.gov/ to the website