Few songs in the traditional canon have as complex a history as the story of Ellen Smith. Let's start with the background, and you'll see why.
That Ellen Smith was murdered there is no doubt. Peter De Graff (or DeGraph; there is no standard spelling of his name), who seems to have been involved with the woman, fled North Carolina, but returned about a year later. He was taken prisoner and tried before one Judge Winston. Convicted in August 1893, an appeal to the state Supreme Court failed, and De Graff was executed.
Nonetheless, there was significant popular doubt about his guilt (he proclaimed his innocence throughout the trial, though some say he made a gallows confession), and Richardson has a report that singing songs about the murder had to be forbidden to prevent riots. (I'd take that with more than a few grains of salt.)
What is true is that the event produced at least two and possibly three ballads, and both became fairly well-known. One, Laws Fl, appears in the collections of Brown, Combs, Fuson, Hudson, and a slew of recordings; it was evidently known throughout the southeast. It is quite substantial, but the ending varies: De Graff is executed, or sentenced to prison, or let off.
The other song, Poor Ellen Smith, is shorter and doesn't tell much of a story; it doesn't show up much in collections, but has been recorded many times, reportedly by Molly O'Day, Estil C. Ball, and the New Lost City Ramblers.
It's at this point that things get incestuous. The first song, Ellen Smith, is sung to the tune of How Firm a Foundation (how's that for a switch: a murder ballad set to a hymn tune). The other -- at least according to the reports I've seen, as well as the recording by Fleming Brown -- has a separate melody. But the two are in the same meter; they can swap verses -- and that's just what they've done. Even though the two began life as quite distinct songs (see the two texts in the Brown collection), recent versions are thoroughly mixed; it's often not possible to tell whether they began life as Ellen Smith or Poor Ellen Smith.
Which brings us to this version, as recorded by Tom Brad & Alice on Holly Ding. They had the text from Tommy Jarrell, born in Mount Airy (near the site of the murder) in 1901. He probably had his version from local tradition, but may have cut it to fit the length of a 78. His version is thoroughly mixed, but seems to have been based on Poor Ellen Smith.
Then Tom Sauber put it to the tune of Ellen Smith (i.e. How Firm a Foundation). Hence this version. It has a twisty enough genealogy to be a Habsburg prince, but it's quite enjoyable.
Incidentally, this version has some differences from the usual texts of the song. For example, De Graff is not usually quoted as wanting to marry her; he "didn't intend to marry her or make her my wife, But I loved her too dearly to take her sweet life."
Who McArthur is I don't know, but his name appears in Brown's 1911 text.
Poor Ellen Smith, and it's how she was found,
Shot through the heart, lying cold on the ground.
Oh, I brushed back my tears when the people all said
That Peter De Graff had shot Ellen Smith dead.
While I would have loved her and made her my wife,
Lord, I loved her too dearly to take her sweet life.
They grabbed their Winchesters, they hunted me down,
But I was away in old Mount Airy town.
They carried me to Winston, my trial to stand
To live or to die as the law may command.
McArthur will hang me, he will if he can;
God knows, if they hang me, I'll die an innocent man.