In his book, The JFK Assassination, James DiEugenio challenged the premise that the Mannlicher-Carcano rifle would not have left residue on Oswald's right cheek: (page 112)
"Former FBI agent Bill Turner did not buy FBI agent Cortland Cunningham's testimony about no residue escaping into the gunman's face. Writing for the magazine American Jurisprudence, Turner conducted his own tests with Vincent Guinn (who, as we have seen, Bugliosi trusts in other matters). Turner and Guinn found that the weapon discharged nitrates in abundance."
The footnote for this paragraph says, "Letter from Turner to Gary Aguilar, July 17, 2007."
Fortunately, my friend Paul Hoch did manage to find a relevant study by Vincent Guinn, which offers a very helpful narrative of what actually happened. The quotation from DiEugenio's book implies that Vincent Guinn and Raymond Pinker's testing of a Mannlicher-Carcano rifle came after Cunningham's testimony to the Warren Commission. In fact, their tests were conducted shortly after November 22, 1963. Bill Turner was not involved in any testing.
It's important to note that Guinn's comprehensive report was written after Turner reported on their conversation. The report covers the company's neutron-activation analysis work through May 31, 1968, and the draft report was not finished until mid-1970.
Some comments about the above excerpt from Guinn's article:
Guinn wrote that "It was generally recognized that the dermal nitrate test was essentially useless," and that "its use might remove any traces of Ba (barium) and Sb (antimony) possibly present."
It was possible that not all the Ba and Sb might have been washed away, and so Guinn decided to do some tests.
Raymond Pinker of the Los Angeles Police Department obtained a Mannlicher-Carcano rifle. It was fired and they obtained two sets of casts. One was treated with the dermal nitrate test, and of the eight casts, only one "gave a clear-cut 'positive' test for nitrates.
The dermal nitrate tests "washed away essentially all of the Ba present," with only a partial loss of the Sb.
Guinn contacted the FBI and asked that the inner surface of the casts be analysed by neutron-activation analysis for antimony. He felt that there still might be enough antimony to indicate if Oswald had fired a rifle.
The FBI took the casts to the Oak Ridge National Laboratory for testing. Significant levels of Ba and Sb were found on all three of Oswald's casts. Unfortunately, the Ba and Sb were found in both the outer and inner surface of each cast. This indicates that the casts had been contaminated and no conclusions could be drawn.
Testing of the Mannlicher-Carcano rifle at General Atomic found that it "did deposit small, but significant, amounts of Ba and Sb on both hands and cheeks of a person who fired the rifle."
DiEugenio is wrong when he writes that "the weapon discharged nitrates in abundance." It discharged a "small, but significant" amount of nitrates.
What's more important is that the dermal test, as used by the Dallas Police department, would not necessarily have detected the nitrates.
True scholarship would have found the actual Guinn article and discussed his findings. Instead, we have a lame attempt to put words into Vincent Guinn's mouth -- words that he never uttered.
Update
Of course, my criticism related to DiEugenio's citation of an article that doesn't seem to exist, not of Bill Turner. But yes, perhaps it is "somewhat unkind to do this type of thing to someone who cannot answer or explain." That certainly describes James DiEugenio.