To add to Vic's posting above,

The Tom Dooley story is told in 2 US histories of the revival - Robert Cantwell's When we were Good and Ronald Cohen's Rainbow Quest. They each show the complex situation about where the Kingston trio might have learned the song from.
Cohen says that Warner first heard Proffitt sing it in 1938, and Warner sang it and recorded it himself on his own album in 1952. Lomax had already published it in Folk Song USA in 1947, attributing Warner. Then The Folksay Trio recorded it. Dave Guard of Kingston Trio said he first heard it sung by a folk-singing psychologist auditioning at the Purple Onion. Guard copied the words from Dick & Beth Best's New Song Fest, published privately in 1948 and commercially in 1955 - this listed no copyright.
After the Kingston Trio's success, Ludlow Music, jointly representing Warner and Lomax, sued Capitol records which had listed the song as "Traditional - arranged Dave Guard". the result was that after 1962 (Tom Dooley was in the charts in second part of 1958) the royalties were split - presumably between Guard/KTrio and Lomax/Warner. In Ronald Lankford's Folk Music USA, he says that Warner then split his share with Proffitt.

But .... the song was recorded by G.B.Grayson, a blind fiddler from Tennessee, in the twenties. He was a descendant of the Grayson who was arrested for the murder.

It may seem strange that the law suit did not involve Proffitt. Or Grayson or his descendants? Or the original composer, whoever he was?

In other words, copyright in traditional music is a minefield.

Derek