Search

This article examines the unreliability of dermal nitrate tests for gunpowder. The method customarily employed was examined for sources of error in technique, but none was found. The technician who performed the tests had been doing them continuously for five years at an average of two pairs of gloves per week. While the many tests were made from a single container, spot checks for possible contamination were made. The study did not enter into the subject of specific chemicals which did interfere with the diphenylamine test. We did, quite by accident, discover that the presence of free chlorine disturbed our results although from a practical standpoint this is not a common problem. The prime consideration was that the presence, on the hands of the deceased, of certain common substances containing nitrates or nitrites did confuse the results insofar as establishing the presence of the products of combustion of gunpowder. Substances when present on the hands of the deceased which are commonly found and are known to give a positive reaction to the diphenylamine test are as follows, tobacco or tobacco ash, fertilizer, pharmaceuticals, leguminous plants and urine among others. It is doubtful that anyone would have sufficient trust in the dermal nitrate test to bring a criminal charge or institute criminal proceedings on the strength of the findings of this test alone. Invariably, there is a mass of other evidence already available and the dermal nitrate test is done with the hope of corroborating or strengthening the already known facts.

The article presents information on 'The Paraffin Gauntlet'--a new technique for the Dermo-Nitrate Test. For a number of years the National Bureau of Identification, Cuba, has used the so-called Paraffin or Dermo- Nitrate Test for systematic investigations in determining whether or not a suspected person had fired a short-barreled firearm or whether a particular hand had come in contact with the gunpowder residues resulting from the discharge of a revolver or pistol. The Vilbiss atomizer, used to produce a fine paraffin spray, is filled up to one-third with the pure paraffin. It is then heated in the atomizer to a temperature slightly higher than its melting point. The hand is laid, with the fingers slightly spread, palm downward on some clean surface, and the dorsal region of the hand is first sprayed with the hot paraffin, taking care not to scald the individual. The layer of pure paraffin must be evenly spread and attain a thickness of at least two millimeters. Without a true reproduction of the shape of the hand, even though the nitrous products of powder combustion are recovered and demonstrated by proper reagents, forensic investigation is not capable of deducing, indicating, or stating that they correspond to the hand that fired the shot or to that which tried to divert it in self-defense.

This section presents police science technical abstracts and notes. In Suppression of Cyanogen Bands in the Direct Current Graphite Arc by Lithium Chloride, by Robert G. Keenan and Charles E. White, the authors use lithium chloride matrix in the cupped carbon to suppress the objectionable cyanogen bands without decreasing the sensitivity of the residual lines of other elements in those wave length regions. In Determination of DDT and Related Substances in Human Fat, by Arnold M. Mattson, Janet T. Spillane et al, the authors a separation method for DDT from biological materials with the use of chromatographic column and determination of the extracted material by absorption spectra. In Preparation of Biological Material for the Determination of Trace Metals. Method for the Destruction of Organic Matter in Biological Material, the method used by the authors consisted of heating biological materials with dilute nitric acid to the point where it left a black char. Upon pretreatment with small amounts of nitric acid brown fumes were evolved and the mixture swelled into a froth and ultimately left a hard black residue. In The Paraffin Test, J. H. Matthews describes the controversial paraffin or dermal nitrate test in a very simple manner.