Electronic Assassinations Newsletter

Issue #2 "New Discoveries in the Recently Released Assassination Files"

Blakey's "Linchpin":
Dr. Guinn, Neutron Activation Analysis, And The Single-Bullet Theory
Part 1

Wallace Milam

The Testimony of Dr. Vincent Guinn: The Misuse of Science


1. In September, 1977, at the request of the House Select Committee on Assassinations (HSCA), the National Archives delivered to Dr. Vincent Guinn, nuclear physicist at the University of California at Irvine, certain bullets and bullet fragments said to be related to the assassination of President Kennedy. [See Appendix F on the issue of whether or not Dr. Guinn had previously done work for the Warren Commission.]

2. Guinn performed neutron activation analysis on the metal at his laboratory during a three-day period in September.

3. On September 8, 1978, one year later, Dr. Guinn testified before the HSCA in open hearings concerning the results of his analysis. Among other things, Dr. Guinn stated:

a. that Mannlicher-Carcano ammunition manufactured by the Western Cartridge company in 1954 tended to be distinctive, especially in the antimony content of the bullets;

b. that it was probable the five relevant fragments said to be related to the wounds of President Kennedy and Governor Connally came from only 2 bullets;

c. that it was "highly probable" that three metal fragments allegedly removed from Governor Connally's wrist came from the bullet allegedly found on a stretcher at Parkland Hospital.

4. Dr. Guinn's testimony was used by the HSCA to buttress the single-bullet theory. Committee counsel Jim Wolf put the proposition to Guinn:

a. WOLF. You can...today state for the first time scientifically that CE-399 [stretcher bullet] did cause the injuries to Governor Connally's wrist?

GUINN. Yes sir, those two match so closely that I would say that such was the case. (HSCA, Vol. I, P. 504)

b. Sources close to the committee reported that Guinn's test results weighed heavily in HSCA's decision to endorse the single-bullet theory in its conclusions. Chief Counsel Robert Blakey was said to have been greatly impressed by Guinn's findings. Since 1979, Blakey, David Belin and others have spoken of the single-bullet theory as a fact, and have stated that it is the "scientific proof" from Guinn's neutron activation analysis which elevated the theory to its new status. In several television debates, Blakey refered to Guinn's conclusions as the "linchpin" which held the single-bullet theory together. His characterization went unchallenged.

c. The importance of the Guinn testimony can thus be demonstrated quite easily:

(i) The single-bullet theory is necessary to explain how Oswald or any other one person could have assassinated the President.

(ii) Guinn's neutron activiation analysis provides the strongest "scientific" proof of the validity of the single-bullet theory.


1. Dr. Guinn was given fragments with the same CE and/or Q numbers which the FBI had used in its 1964 NAA tests, but none of these "same" fragments weighed the same!

2. HSCA implied that this was due to alteration of the fragments during the previous tests:

a. "There are differences in the count and weight of the materials examined by the FBI and Dr. Guinn. This is attributable to the character of the FBI tests and to the fact that the FBI disposed of the samples examined after the tests." (HSCA Report, p. 599, note 33)

b. No footnotes or other citation offers proof of this explanation.

c. The implication here is that the FBI's tests were of a kind which destroyed some of the samples being tested. However, Dr. Guinn's testimony clearly disputes this explanation:

FITHIAN. You have said this whole process that you go through does not destroy the material, is that correct?

GUINN. That is correct.

FITHIAN. Now, then, did you test exactly the same particles that the FBI tested in 1964?

GUINN. Well, it turns out, I did not, for reasons I don't know, because as they did the analysis, they DID NOT destroy the samples either. [emphases added]


GUINN. The particular little pieces that they analyzed, I could just as well have analyzed over again, but the pieces that were brought from the Archives-which reportedly, according to Mr. Gear--were the only bullet-lead fragments from this case still present in the Archives-did not include any of the specific little pieces that the FBI had analyzed. Presumably those are in existence somewhere, I am sure nobody threw them out, but where they are I have no idea.

FITHIAN. And the 1964 equipment wouldn't have consumed them either?

GUINN. No. (HSCA, I, pp. 561-562. emphases added)

3. Thus, we have these improbable circumstances:

a. The FBI tested certain metal fragments with certain identification labels (CE's/Q's) in 1964.

b. The FBI's tests were not of a kind which would have used up any of the fragments.

c. The National Archives passed on to Dr. Guinn an entirely different set of fragments-with the same CE and/or Q numbers, alleging them to be related to the Kennedy case.

d. The Archives told Dr. Guinn that these were the only bullet-lead fragments remaining there from the case.

e. HSCA's explanation for this remarkable state of affairs is contradicted by Dr. Guinn and unsupported by any documentation whatsoever.

4. After his testimony before the committee was completed, Dr. Guinn talked with several people in the hallway outside the committee room. His remarks were recorded on tape, and they are noteworthy. Among other things, Dr. Guinn said:

a. It was not until the fragments from the National Archives arrived at his California lab that he discovered he was testing fragments different from those tested by the FBI.

b. None of the weights matched those of the 1964 test fragments.

c. It would have been easy to deliberately falsify the evidence to be tested:

"Possibly they would take a bullet, take out a few little pieces and put it in the container, and say, 'This is what came out of Connally's wrist.' And naturally, if you compare it with 399, it will look alike... I have no control over these things."


Both in his testimony before HSCA and in a paper which he submitted to the committee (JFK-F331), Dr. Guinn outlined the basics of neutron activation analysis (NAA) and the procedures he used in studying the fragments from the National Archives:

1. First, Guinn grouped the materials: the unfired Mannlicher-Carcano round allegedly from the rifle found on the sixth floor and the "mashed bullet" allegedly fired at General Walker became Group II. Those fragments "reportedly found in or near the limousine and its occupants" were designated Group I. Eight items were included in this group:

a. a piece of curb from Dealey Plaza (Q609)

b. a fragment reportedly found in the front seat of the limousine (Q3, CE-569)

c. particles scraped from the windshield of the limousine (Ql5, CE-841)

d. a whole bullet allegedly found on a stretcher at Parkland Hospital (Ql, CE-399)

e. a large bullet fragment from the front seat of the limousine (Q2, CE-567)

f. two fragments removed from President Kennedy's brain during autopsy (Q4-5, CE-843)

g. three small fragments reportedly removed from Governor Connally's wrist during surgery (Q9, CE-842)

h. fragments from the rear floor of the limousine (Ql4, CE-840)

2. Guinn soon decided that three of his samples were not suitable for NAA. The vial supposedly containing the windshield scrapings was empty, the curbing sample consisted only of a smear, and one of the front seat fragments (CE-569), consisted only of the copper Jacketing, with no lead present. None of these three samples consisted of the requisite 5 milligrams of lead necessary for NAA.

3. The remaining samples were washed with acetone and deionized water and placed in polyethylene vials, which were then inserted into a nuclear reactor. Apparently, Guinn did not do any control testing, that is, he did not take 2 pieces from the same exhibit and measure their antimony and/or silver content to assure himself that the cylindrical lead core from which these samples came was homogeneous with regard to these key elements throughout. This failure becomes crucial when his purported results are presented.

4. Inside the reactor, the samples were bombarded with neutrons, some of which were captured by the nuclei of the various kinds of atoms present in the samples, making these atoms radioactive.

5. These radioactive atoms then began to decay at a specific rate or half-life.

6. In decaying, their nuclei gave off radiation-beta particles and gamma rays.

7. It was the gamma rays which Guinn used in making his analysis. A sensitive germanium lithium-drift semiconductor gamma ray detector was used. Gamma rays emitted from the nuclei of the atoms of each element present have energies specific for that element and thus showed up at the same point or "channel" on the analyzer. A "spike" at a discrete point on the "channel" indicated the atomic source or element, while the area of the "spike" indicated the quantity of the element present in the sample.

8. A mathematical formula allowed the quantity of each radioactive element to be expressed in parts per million (ppm) found in the sample.

9. The theory behind neutron activation analysis is that irradiation and decay produce qualitative and quantitative data on all elements present in a given specimen. In the case of bullets and bullet fragments, NAA may allow the identification of the various elements present in the bullet lead and the amounts of each element present.

10. Various "trace elements" in addition to lead are found in "bullet lead," the core portion of bullets. These elements may be present as a result of contamination or may be added in order to change the nature of the bullet.

11. Dr. Guinn's instruments detected and measured the amounts of 8 elements present in bullet lead-antimony, silver, copper, magnesium, chlorine, sodium, manganese, and aluminum.

12. Dr. Guinn stated on several occasions (both in his paper and in his testimony) that antimony was the most important trace element in comparing bullet samples through NAA, with silver of slightly less significance. Copper was also usually present, but often as jacket contamination which had found its way into the core sample. The other five elements were found to be present from time to time as a result of contamination of the sample.

13. Thus, the first of two overriding hypotheses on which the principle of neutron activation analysis of bullet lead depends is that it possible to accurately measure the amounts of antimony, silver, and copper in a given sample of bullet material.

14. The second hypothesis is that bullets of different calibers, from different manufacturers, from different manufacturing lots, and from different individual bullets within a given lot or box have distinctive and unique amounts of antimony, silver and copper.

15. The first hypothesis, if correct, would allow the creation of a body of data. The second hypothesis, if correct, would allow scientific interpretation of the meaning of the data. Together, they would, in theory, allow the grouping or the separation of bullet fragments as to origin. At a crime scene, recovered bullet fragments could be accurately attributed to or separated from one another. Fragment A could be said to have come from the same bullet as Fragment B, or all the fragments present could be said to have come from the same box of ammunition. The combining of these two hypotheses gives NAA its potential value as a forensic tool.


1. In actual practice, NAA proved far less than a perfect forensic tool. Gamma rays could be counted accurately using the increasingly-sophisticated equipment. However, the pattern of trace elements present in various bullet leads proved not to be distinctive for individual brands, lots or bullets.

2. In 1968, Dr. Guinn and M. R. Lukens presented a paper,, "Comparison of Bullet Lead Specimens by Nondestructive Neutron Activation Analysis," before the American Academy of Forensic Sciences in Chicago. The paper offers insights into the state of NAA at the time.

3. Guinn and Lukens reported "Progress has been made toward the establishment of probabilities that, within the bounds of analytical precision, (1) bullets of common origin will have the same composition, and (2) bullets of different origins will have different composition." (Guinn and Lukens, Journal of Forensic Sciences, Vol. 16, No. 3, p. 30)

4. Antimony had been pinpointed as the most significant trace element in bullet lead, and the authors reported the antimony content of 36 different types of bullets from a variety of manufacturers, ranging from 0.22 caliber to 0.45 caliber. As many as 20 bullets from a given box of rifle ammunition were analyzed for antimony content, and several 0.38 caliber bullets of various makes had been fragmented into from 10-12 pieces per bullet, with antimony measurements made of each of the fragments from different portions of the same bullet. (See Appendix B)

5. In their research, Guinn and Lukens identified a persistent problem for NAA: many types of bullets had overlapping antimony values. A Peters 0.22 and a Remington 0.22 contained virtually the same amount of antimony as a trace element. In some cases, the other trace elements, such as copper and silver, could be used to help distinguish between bullets whose antimony contents were overlapping, but in many other cases, this was not possible. Guinn and Lukens wrote in the conclusion to their article:

"Thus while it can be said with confidence that bullets with different antimony concentrations have different origins, the present data indicate that there is a 28% chance that whole bullets with the same antimony level may have a different origin..." (Journal of Forensic Sciences, Vol. 16, No. 3, p. 306)

6. In 1970, Dr. Guinn published on NAA again, this time with Lukens, H. L. Schlesinger and R. P. Hackleman in "Forensic Neutron Activation Analysis of Bullet-Lead Specimen," for the Atomic Energy Commission.

7. By now, 230 samples of bullet leads from 75 different lots of bullets had been examined. Three elements were now identified as having the greatest diagnostic significance-antimony, copper, and arsenic, in order of their analytical value.

8. But the problem of overlapping was still there. Antimony concentrations for many types of bullet lead fell within a range of 0.7-0.8% of the sample, and the copper and arsenic concentrations tended (a) overlap in the same manner as antimony and (b) to have large standard deviations.

9. In the end, Guinn and his colleagues conceded that "less than half of the 75 lots of bullets were uniquely characterized by the concentrations of Sb (antimony), Cu (copper) and As (arsenic) ... As a result of the foregoing it can be said that a significant difference in concentration of any one of the three elements between two bullet specimens indicates that they came from different lots, but that matching concentrations of all three elements does not indicate that two bullets came from the same lot." The chemists concluded by recommending that manufacturers might add a "unique combination trace element tag" to each lot of bullets, in order to assist with NAA.


1. In 1972, Dr. Guinn first turned his attention to Mannlicher-Carcano ammunition manufactured by the Western Cartridge Company, the type supposedly used in the assassination of President Kennedy.

2. Dr. John Nichols of Kansas University contacted Guinn and offered him bullets from each of 4 production lots made by WCC in 1954. Subsequently, Nichols sent Guinn a total of 14 WCC bullets, 2 from one production lot and 4 each from three other production lots. [There are no indications in either Guinn's testimony before HSCA or his technical writings that he ever examined any WCC Mannlicher ammunition other than these 14 bullets from Nichols.]

3. During 1973, 1974 and 1975, Guinn did NAA on the materials sent him. At the time he performed his tests for HSCA, Guinn had not published any findings concerning his work. [Guinn submitted a paper at the time of his testimony in September, 1978, dated "September, 1978," and he and Nichols published "Neutron Activation Analysis of Bullet Lead Specimens: The President Kennedy Assassination" in Number 28 of Transactions of the American Nuclear Society, also dated 1978.]

4. Guinn told the committee that he had found WCC Mannlicher bullets to be unique in certain respects:

a. WCC Mannlicher bullets had very low antimony contents.
Guinn explained that antimony is sometimes deliberately added to bullet-lead in order to "harden" it. "Hardened" bullets often contain from 0.4% to as much as 5% antimony. A 0.4% addition of antimony in the hardening process would yield parts-per-million concentrations of antimony in the range of 4000. Guinn reported that "virgin lead" could be used to produce a bullet with very low antimony content-within ranges he placed at only 10-20 ppm. (HSCA, Vol. I, p. 544) Guinn stated that although WCC Mannlicher rounds were not produced of virgin lead, they were very low in antimony content: "They are definitely unhardened bullets." (HSCA, Vol. I, p. 494)

b. WCC Mannlicher bullets showed "tremendous" antimony and other trace element variations from one lot to the other and also between bullets taken from the same box. Unlike the earlier problem encountered--overlapping trace element values for various makes of bullets, Mannlicher-Carcano bullets returned values "all over the place"

GUINN. The other unusual feature of the WCC Mannlicher Carcano is that there seems to be no uniformity within a production lot. That is, even when we would take a box of cartridges all from a given production lot, take 1 cartridge out and then another and then another and then another, all out of the same box--boxes of 20, these were-and analyze them, they all in general look different, and widely different, particularly in their antimony content ... This is not true of most bullet leads that we have ever looked at before, which are very uniform. In general, if you take most boxes of ammunition-and we published on this; it is in the literature-take a bunch of them out, you can't tell one from the other. They all look like little carbon copies even to activation analysis, but not so with the Mannlicher-Carcano." (HSCA, Vol. I, pp. 494-495)

Guinn offered an explanation for this phenomenon in his report to HSCA. While some bullet leads are deliberately hardened with antimony and other, virgin leads are kept free of any antimony except small amounts of accidental contaminants, other bullet leads, including those from WCC, are made from lead which has been recycled from other bullets or other lead sources, such as storage batteries.. This "used lead" may be a complex mixture of bullet-leads which were hardened and of bullet leads which were virgin (and of even previously recycled leads) and lead which was never a part of any bullet. As a result, the antimony content could vary-in Guinn's words-"tremendously"-in any portion of the recycled bullet lead, from lot to lot and from bullet to bullet within a lot.

c. Within individual WCC Mannlicher bullets, there was homogeneity of bullet lead trace elements. In contrast to the "tremendous" variations found bullet to bullet, "...you simply do not find a wide variation in composition within individual WCC Mannlicher-Carcano bullets..." (HSCA, Vol. I, p. 505), In the paper he submitted, Guinn wrote "Results of UCI [University of California Irvine] background studies of WC bullet lead indicates a wide range of Sb values, from bullet to bullet, but reasonable homogeneity within an individual bullet." (HSCA, Vol. I, p. 546)

This becomes the key point of the entire issue of NAA. It is this claim which allowed Guinn to make the matches of bullets and fragments in the Kennedy case. It was this claimed characteristic of WCC Mannlicher ammunition which brought Guinn to Washington to testify and which gave his testimony its meaning. [More on the issue of homogeneity within Mannlicher bullets in Part 2].

Go to appendix A

Go to appendix B

Go to appendix C

Go to appendix D

Go to appendix E

Go to appendix F

Go to appendix G

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