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Report of the Committee on Ballistic Acoustics (1982)

Chapter: V. EVALUATION OF THE FBI REPORT

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Suggested Citation:"V. EVALUATION OF THE FBI REPORT." National Research Council. 1982. Report of the Committee on Ballistic Acoustics. Washington, DC: The National Academies Press. doi: 10.17226/10264.
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Page 32

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be retained, and some typographic errors may have been accidentally inserted. Please V. EVALUATION OF THE FBI REPORT 32 V. EVALUATION OF THE FBI REPORT Although the Committee agrees with the “Findings” in the November 19, 1980, FBI report4, it disagrees with one of the arguments used to justify the Findings. It considers invalid the criticism of the WA report on the basis of the high value of the binary correlation coefficient found by the FBI for a match between the supposed grassy knoll shot and one of the recorded gunshots in the unrelated later shootings at Greensboro, North Carolina. Although the FBI obtained a high value of the correlation coefficient, that value was not nearly so significant as the one obtained by WA, which involved many more “time windows” (90 windows were used although this number was erroneously reported as 45 on page 76 of the BRSW report) and 39 Greensboro shots were available from which the most favorable could be selected. Although the Committee considers this particular FBI argument against the BRSW/WA report to be invalid, the Committee, for the reasons discussed in this report, agrees with the FBI conclusions. use the print version of this publication as the authoritative version for attribution.

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At the time of the assassination of President Kennedy, the Dallas police recorded sounds from an open microphone; these sounds have been previously analyzed by two research groups at the request of the House Select Committee on Assassinations. Both groups concluded with 95% probability that the recordings contained acoustic impulses which provide evidence for the existence of a shot from the grassy knoll area of Dealey Plaza. On the basis of these results and since shots definitely were fired from the Texas School Book Depository, the House Committee concluded that "scientific acoustical evidence establishes a high probability that two gunmen fired at President John F. Kennedy."

Report of the Committee on Ballistic Acoustics studied these reports and the Dallas Police recordings on which they are based. This book reviews the methodology employed in the evaluations of the recorded acoustic data and of the conclusions about the existence of a shot from the grassy knoll. According to this report, the acoustic analyses do not demonstrate that there was a grassy knoll shot, and in particular there is no acoustic basis for the claim of 95% probability of such a shot. The acoustic impulses attributed to gunshots were recorded about one minute after the President had been shot and the motorcade had been instructed to go to the hospital. Therefore, reliable acoustic data do not support a conclusion that there was a second gunman.

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