Don Thomas, the scientist who revived the debate about the House Select Committee on Assassinations "acoustical analysis" which found a grassy knoll shot, has written a new essay.

Featured on the Mary Ferrell Foundation website is Acoustics Overview and History, in which Thomas traces the history of the science and controversy regarding the police dictabelt which the HSCA determined had recorded the gunfire in Dealey Plaza.

In Part 1, Thomas discusses the basic facts of the Dallas police recordings and their authenticity, and then reviews the tests the HSCA conducted. Part 2 makes the case that the analysis which identified the shots is powerfully confirmed by other evidence which corroborates the order and timing of the shots. In part 3, Thomas discusses the NRC Report and other challenges to the acoustical findings.