Editing Single-bullet theory (section)

==Neutron activation analysis of bullet fragments==
===Original bullet lead analysis by Vincent Guinn===
Warren Commission documents released after the publication of its report revealed that the FBI had arranged for bullet CE&nbsp;399 and the various fragments found in the car and in Governor Connally's wounds to be examined using [[neutron activation analysis]] (NAA). NAA is a precise, non-destructive method of determining the relative concentrations of trace elements in a sample of matter. The data from the tests performed for the FBI were inconclusive as to the origins of the fragments.<ref>Letter from J. Edgar Hoover to Commission Counsel Lee Rankin, July 8, 1964. Exhibit F-332A, 1 HSCA 558 [http://www.history-matters.com/archive/jfk/hsca/reportvols/vol1/html/HSCA_Vol1_0281b.htm]</ref>

In 1978 the HSCA asked physicist Vincent P. Guinn to review the NAA data and conduct new tests. Guinn did so and presented his results and analysis to the Committee. Guinn stated that initially he agreed with the earlier conclusion. After examining the old and new NAA data further, he concluded that all the fragments probably came from two bullets, one of which was the whole bullet, CE&nbsp;399.<ref>{{cite web|url=http://www.history-matters.com/archive/jfk/hsca/reportvols/vol1/html/HSCA_Vol1_0248a.htm |title=History Matters Archive - HSCA Hearings - Volume I, pg |publisher=History-matters.com |access-date=August 3, 2010}}</ref>

Guinn compared antimony concentrations of Exhibits CE&nbsp;840, 843 and 567 with that of Exhibits CE&nbsp;399 and CE&nbsp;842 and concluded that the data supported the single-bullet theory in that all the bullet lead in the car and wounds originated from no more than two bullets.<ref name="history-matters.com">{{cite web|url=http://www.history-matters.com/archive/jfk/hsca/reportvols/vol1/html/HSCA_Vol1_0269a.htm |title=History Matters Archive - HSCA Hearings - Volume I, pg |publisher=History-matters.com |access-date=August 3, 2010}}</ref>

===Conclusions about the single-bullet theory from the NAA analysis===
Whether the NAA data can be used to actually exclude the possibility that there were fragments from more than two bullets in the wounds and the car has been the subject of controversy.

Ken Rahn of the University of Rhode Island,<ref name="karws.gso.uri.edu">{{cite web |url=http://karws.gso.uri.edu/JFK/scientific_topics/NAA/NAA.html |title=Neutron-Activation Analysis |publisher=Karws.gso.uri.edu |access-date=August 3, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100520041055/http://karws.gso.uri.edu/jfk/scientific_topics/NAA/NAA.html |archive-date=May 20, 2010 }}</ref> a chemist and meteorologist who has a long-standing interest in the Kennedy Assassination, maintains that the NAA data excludes a "three bullet hit" and proves the single-bullet theory actually occurred. His analysis was published in 2004<ref>{{cite journal |id={{INIST|16161314}} |doi=10.1023/B:JRNC.0000040876.55194.3a |title=Neutron activation and the JFK assassination, Part I. Data and interpretation |year=2004 |last1=Rahn |first1=K. A. |last2=Sturdivan |first2=L. M. |journal=Journal of Radioanalytical and Nuclear Chemistry |volume=262 |issue=1 |pages=205–13|citeseerx=10.1.1.578.755 |s2cid=98396920 }}</ref> co-authored with Larry Sturdivan, a Warren Commission and HSCA ballistics expert.

Rahn/Sturdivan say that the possibility that the wrist fragment CE&nbsp;842 (with an antimony concentration of 797±7&nbsp;ppm) did not come from the base of the whole bullet CE&nbsp;399 (the sample from which had an antimony concentration of 833±9&nbsp;ppm) is so statistically improbable as to be excluded as a reasonable possibility.

Contradicting this conclusion, in an article published in July 2006 in the ''Journal of Forensic Sciences'' by Erik Randich and Patrick M Grant,<ref>{{cite journal |doi=10.1111/j.1556-4029.2006.00165.x |title=Proper Assessment of the JFK Assassination Bullet Lead Evidence from Metallurgical and Statistical Perspectives |year=2006 |last1=Randich |first1=Erik |last2=Grant |first2=Patrick M. |journal=Journal of Forensic Sciences |volume=51 |issue=4 |pages=717–28 |pmid=16882211|s2cid=20614842 |url=https://digital.library.unt.edu/ark:/67531/metadc890664/ }}</ref> the authors took a significantly different view of the NAA data and the metallurgical profile of the Carcano ammunition. The authors found errors in the analysis by Guinn:

<blockquote>Thus, elevated concentrations of antimony and copper at crystallographic grain boundaries, the widely varying sizes of grains in MC bullet lead, and the 5–60&nbsp;mg bullet samples analyzed for assassination intelligence effectively resulted in operational sampling error for the analyses. This deficiency was not considered in the original data interpretation and resulted in an invalid conclusion in favor of the single-bullet theory of the assassination.</blockquote>

Randich and Grant concluded:

<blockquote>The end-result of these metallurgical considerations is that, from the antimony concentrations measured by VPG [Vincent P. Guinn] in the specimens from the JFK assassination, there is no justification for concluding that two, and ''only'' two, bullets were represented by the evidence.</blockquote>

The conclusion of Randich and Grant had been advanced earlier by Arthur Snyder of the Stanford Linear Accelerator Laboratory in a paper written in 2001.<ref>{{Cite web| url=http://karws.gso.uri.edu/JFK/Scientific_topics/NAA/Snyder_critique.pdf | title=On Ken Rahn's Statistical Analysis of the Neutron Activation Data in the JFK Assassination | access-date=January 25, 2007 | url-status=dead | archive-url=https://web.archive.org/web/20070226005343/http://karws.gso.uri.edu/JFK/scientific_topics/naa/Snyder_critique.pdf | archive-date=February 26, 2007}}{{full citation needed|date=December 2013}}</ref>

In August 2006 Ken Rahn wrote a response critical of the Randich/Grant paper on his website<ref name=Rahn>[http://karws.gso.uri.edu/JFK/scientific_topics/NAA/review_of_rg/Review.html Review of Randich and Grant's article on NAA<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20120220085652/http://karws.gso.uri.edu/JFK/scientific_topics/NAA/Review_of_RG/Review.html |date=February 20, 2012 }}</ref> claiming that Randich and Grant did not analyse the data correctly:

<blockquote>Both sections of the article failed to make their case. The metallurgical section contained a huge gap in its logic (proposing an explanation but failing to support it quantitatively), and predicted at least two features of the elemental data that were the opposite of that actually observed. The statistical section started well, but stumbled when it confused heterogeneity with analytical uncertainty and when it used confidence intervals instead of difference in means to assess the separation of the two groups of crime-scene fragments. Fixing these two errors gave the opposite result, i.e., confirmed that the groups were distinct.</blockquote>

Patrick Grant defended his and Erik Randich's paper against Rahn's critique in an article entitled ''Commentary on Dr. Ken Rahn's Work on the JFK Assassination Investigation'' and posted it on the MaryFerrell.org website.<ref>{{cite web|url=http://www.maryferrell.org/wiki/index.php/Essay_-_Commentary_on_Dr_Ken_Rahns_Work_on_the_JFK_Assassination_Investigation |title=Commentary on Dr. Ken Rahn's Work on the JFK Assassination Investigation |publisher=MaryFerrell.org |access-date=February 18, 2015}}</ref>

===Forensic use of compositional bullet lead analysis===
The technique used by Guinn to analyse the bullet lead from the JFK assassination was a form of what has become known as Compositional Bullet Lead Analysis (CBLA). Until 2004 the FBI used this technique to determine whether a crime scene bullet lead sample came from a particular box of ammunition or a particular batch of bullets. Guinn claimed that with the JFK bullet fragments, the technique could be used to identify the exact bullet the fragments came from.

The validity of CBLA was discredited in a 2002 paper ("A Metallurgical Review of the Interpretation of Compositional Bullet Lead Analysis" (2002), 127 Forensic Science International, 174–191)<ref>http://www.dufourlaw.com/JFK/randich_2002_FSIpaper.pdf{{full citation needed|date=December 2013}}</ref> co-authored by Randich and by former FBI Chief [[Metallurgist]], William Tobin.

The 2002 Tobin/Randich paper prompted the National Academy of Sciences (Board on Chemical Science and Technology) to review the science of bullet lead analysis. In a report in 2004<ref>{{cite book |url=https://archive.org/details/forensicanalysis0000nati |title=Forensic Analysis Weighing Bullet Lead Evidence |publisher=Books.nap.edu |date=October 11, 2002 |access-date=August 3, 2010 |doi=10.17226/10924 |isbn=978-0-309-09079-7 |url-access=registration }}</ref> the NAS found the scientific basis for matching bullet sources from the analysis of bullet lead composition as practiced by the FBI was flawed. As a result of that report, courts appear to have stopped accepting this evidence<ref>{{cite web|url=http://www.abanet.org/crimjust/cjmag/21-4/ScientificEvidence.pdf |title=Criminal Justice Section &#124; Criminal Justice Section |publisher=Abanet.org |access-date=January 5, 2013}}</ref> and the FBI has stopped using bullet lead analysis for forensic purposes.<ref>{{cite web|url=https://www.fbi.gov/news/pressrel/press-releases/fbi-laboratory-announces-discontinuation-of-bullet-lead-examinations
|title= FBI Laboratory Announces Discontinuation of Bullet Lead Examinations|publisher = FBI National Press Office}}</ref>

The NAS report on CBLA, and its relevance to the Guinn's analysis of bullet lead in the JFK assassination, is the subject of comment by Randich and Grant in their 2006 paper at page 719.<ref>http://www.dufourlaw.com/JFK/JFKpaperJFO_165.PDF{{full citation needed|date=December 2013}}</ref>