Ben Stone, portrayed by Michael Moriarty, was the Executive Assistant District Attorney for Manhattan County in the first four seasons of Law & Order (1990).
Mitochondrial DNA depletion syndrome (MDDS) is a recessive genetic disorder that causes the DNA in cell mitochondria, the cell organelle responsible for converting chemical energy into food that sustains cell functions. There are several different types of MDDS, these syndromes affect tissue in the muscle, liver, or both the muscle and brain, respectively. There is no known cure and most forms of the condition are almost always fatal, especially the type of MDDS that affects muscle, most children with this type die within a few years of birth, children can survive to see their teenage years but it is very rare. The form of MDDS that causes brain degeneration is the least deadly form, some people with it have been known to survive to adulthood, though they have severely limited cognitive function.
Sam Waterston begins the episode with a eulogy. His first words are, "In my younger and more vulnerable years. . . " Those are the exact words that open the novel The Great Gatsby (1974). Sam Waterston played Nick Carraway in that film, and he began the movie with the exact same words.
This is Sam Waterston's first appearance as Jack McCoy since the Law & Order (1990) series finale Rubber Room (2010) almost eight years earlier.
The last lines of Jack McCoy's eulogy "And flights of angels sing thee to thy rest" is from Shakespeare's Hamlet.