Mr. Redlich. Could you describe briefly, without reference to the specific evidence that is under investigation here, the nature of this technique?
Mr. Gallagher. Neutron activation analysis involves subjecting small samples to a beam of sub-atomic particles known as neutrons. Elements within the sample having been bombarded by neutrons are transformed in many instances to radioactive atoms. These radioactive atoms will decay and emit characteristic radiations. By studying the emitted radiations, one can determine and trace quantities of elements in specimens.
Mr. Redlich. This is a technique whereby certain elements are made radioactive as a result of being bombarded by neutrons; is that correct?
Mr. Gallagher. Yes, sir.
Mr. Redlich. This enables you to isolate certain elements for purposes of analysis; is that correct? Let me rephrase the question: Does this enable you to determine the presence of certain elements for purposes of analysis?
Mr. Gallagher. This enables you to determine and to measure the quantity of certain elements in a given specimen.
Mr. Redlich. What is the advantage of the neutron activation technique over other methods of determining the presence of certain elements?
Mr. Gallagher. Well, this method of analysis, because of its extreme sensitivity, offers a great advantage over more conventional procedures. Furthermore, chemical treatments of your samples subsequent to activation do not distort your results by contamination. If an acid, for example, is added to a specimen after irradiation which is under study for the presence of antimony, and the acid itself contains antimony, it will not contain a radioactive form of antimony, and this is the form which is measured during the analysis.
Mr. Redlich. Has neutron activation analysis been used in criminal investigation work, to your knowledge, Mr. Gallagher?
Mr. Gallagher. It has been used in criminal investigative work.