Then I made a comment that in some very specific situations a mitochondrial DNA test might be useful. The other commenter thought mitochondrial DNA tests were a total waste of time. I reiterated that it is quite useful under very specific circumstance. I did, of course, mention my own reason for doing a mitochondrial test. Initially I wanted to learn the mitochondrial haplogroup to put to rest one of those full-blooded Indian rumors in my line. The haplogroup came back Western European so my goal was achieved. I also hoped it would help identify my 3g-grandmother's mother. That result is currently on hold as I need to work much more with the results to achieve it.
However, the discussion made me realize I needed some good examples of how mitochondrial DNA solved genealogical problems. My mind immediately went to Elizabeth Shown Mills' great article, "Testing the FAN Principle Against DNA: Zilphy (Watts) Price Cooksey Cooksey of Georgia and Mississippi," which first appeared in National Genealogical Society Quarterly in June 2014 and is now available on the author's Historic Pathways site. This case used all types of DNA, providing genealogists a great model for DNA research. I am sure I saw another published case study demonstrating mitochondrial DNA as a genealogical tool, but I could not remember it.
However, I did find a blog post by Roberta Estes, "Mitochondrial -- the Maligned DNA," which shows how mitochondrial DNA was used to resolve of which wife of a male ancestor the tester was a descendant.
I also found a somewhat technical but useful post by Blaine Bettinger, "An mtDNA Journey -- Discovering My mtDNA in a Research Paper," describing some of the surprises discovered in his own mitochondrial DNA and how he discovered his mtDNA in a research study defining his haplogroup.
I thought I'd toss the question out for others. Do you know of another example of a published case study involving mitochondrial DNA in DNA research? Has mitochondrial DNA been useful in your own line?
Bettinger, Blaine. "An mtDNA Journey -- Discovering My mtDNA in a Research Paper," The Genetic Genealogist, 30 July 2015 (http://thegeneticgenealogist.com/2015/07/30/a-mtdna-journey-discovering-my-mtdna-in-a-research-paper/ : accessed 25 June 2016).
Estes, Roberta. "Mitochondrial -- the Maligned DNA," DNAeXplained - Genetic Genealogy, 29 March 2014 (https://dna-explained.com/2014/03/29/mitochondrial-the-maligned-dna/ : accessed 25 June 2016).
Mills, Elizabeth Shown. "Testing the FAN Principle Against DNA: Zilphy (Watts) Price Cooksey Cooksey of Georgia and Mississippi." National Genealogical Society Quarterly 102 (June 2014): 129-152; image copy, Historic Pathways (https://www.historicpathways.com/download/ZilphyArticle072915.pdf : accessed 25 June 2016).