John I. Thornton

A Critical Analysis of Quantitative Fingerprint Individuality Models

A critical analysis is presented of the seven principal models previously proposed for the quantitative assessment of fingerprint individuality. Although these models have been developed over a long period of time, there has been no systematic or comprehensive review of all seven models; indeed, two very significant models have escaped the attention of contemporary investigators altogether. The present work compares and contrasts these various models. Each of the models that has been proposed is described and discussed critically in relationship to the fingerprint comparison process. None of the models previously advanced is found to incorporate the essential features of fingerprint comparison. These essential features are summarized in the context of a quantitative fingerprint individuality model.

Kinetics of heroin deacetylation in aqueous alkaline solution and in human serum and whole blood

A kinetic study of heroin hydrolysis in alkaline aqueous solution at room temperature was conducted by a gas chromatographic method to measure the consecutive reactions of diacetylmorphine to monoacetylmorphine and of monoacetylmorphine to morphine. A first-order reaction was observed in both instances, and the rate for the deacetylation of heroin was greater than that of monoacetylmorphine. The rates of in vitro hydrolysis of diacetylmorphine in human whole blood and in serum were compared by the same method. Diacetylmorphine was hydrolyzed twice as rapidly in blood as in serum. While morphine was an end product of hydrolysis in the blood, it was absent in the serum.

Enzymatic Characterization of Soil Evidence

Soils is most assuredly an important type of physical evidence; if one can establish that soil on the shoes or clothing of a suspect matches that of a crime scene it will lend support to a hypothesis that the suspect had, in fact, visited the scene. Likewise, comparison of soil from the tires or the undercarriage of an automobile with the soil from a particular location may establish with greater or lesser certainty that the automobile was at one time present at the location. Furthermore, soil evidence is more likely to be encountered in those offenses against persons or property which society deems most severe. Equally important is that soil evidence, properly examined and properly interpreted, may serve an exclusionary purpose and exonerate the innocent. Erratum to this paper appears in 21(2).

The Identification of Marijuana

The chemistry of the phenolic constituents of the resin from the leaves and flowering tops of the marijuana plant is reviewed, and discussed in terms of possible chemical precursors to synthetic tetrahydrocannabinol which may be encountered. The Duquenois test is studied and support presented for the hypothesis that the mechanism of the test is in part an electrophilic substitution type of reaction. Evidence is presented to suggest that the product of the Duquenois reaction is not a reticulated polycondensate, but exists as a resole. A study is made of the Levine modification of the Duquenois test involving a terminal extraction of the color with chloroform. The ability of Duquenois reactants to extract into chloroform is related to the structure of the phenolic constituents of the resin. Thin-layer chromatographic separation of the major constituents of marijuana resin is described, as well as the infrared absorption of tetrahydrocannabinol isomers. The occurrence of cystolith hairs are an important criterion in the identification of marijuana leaf fragments. Cystolith hairs, however, occur among several dicotyledonous families, notably the Moraceae, Boraginaceae, Loasaceae, Ulmaceae, and Cannabinaceae. Since these develop in different forms in these families, marijuana can be differentiated in many cases. However, in other cases where similarity in cystolith development occurs, other morphological features, such as the trichomes on the other side of the leaf are helpful in differentiation. In any event, cystolith hairs cannot be used as a sole criterion for marijuana identification. The Duquenois-Levine test is found to be useful in the confirmation of marijuana, since none of the 82 species possessing hairs similar to those found on marijuana yield a positive test. Where marijuana cannot be morphologically delineated, thin-layer chromatographic methods are indicated.

The chemistry of death by gunshot

Abstract When a firearm is discharged, a complex series of events takes place within an interval of approximately 1 millisecond. Many of these events are associated with chemical as opposed to mechanical processes, and an understanding of these processes, and of the materials involved in these processes, may be of value in the reconstruction of the factual circumstances at the instant of discharge. These chemical processes include the formation of uprange and downrange gunshot residues of several diverse sorts. Proper analysis and interpretation of gunshot residues and other components of ammunition may provide useful information in the investigation of shooting incidents.

Glass fracture analysis. A review.

Abstract A discussion is presented of the forensic interpretation of annealed glass fracture. The processes of glass fracture are given, the nature and formation of glass as a brittle isotropic solid is discussed, and the mechanical strength of glass is considered in terms of its atomic bond strengths and external flaws. Major modern theories of glass fracture propagation are reviewed, and the relationships of stress conditions to fracture surface properties are developed.

Glass Fracture Mechanism—A Rethinking

Conventional attitudes within the forensic science community concerning the fracturing of glass center around tensile failure of the glass, frequently depicted as a “bending” of the glass. While this is not conceptually incorrect, it represents only one case of a more universal phenomenon in which the tensile failure of glass does not necessarily involve any significant deflection of the glass. Tensile failure can be achieved with either quasi-static or dynamic loading of the glass. In quasi-static loading, tensile failure will initiate a fracture at the weakest point (that is, the locus of a Griffith crack), but the surfaces of this crack may be in optical contact, and thus no perceptible deformation of the glass would be required before failure. A consideration of dynamic loading is necessary to explain the “cratering” effect observed in moderate- to high-velocity projectile impact. In sharp dynamic loading (for example, a bullet impact) the tensile stress is provided by the reflection and subsequent interference of the compression waves which precede the passage of the projectile; this particular type of stress results in Hopkinson fractures, a multiplicity of which creates a crater. The dimensions and chamfering of projectile craters are a manifestation of the crack velocity propagation, and are not inherently a function of projectile velocity or caliber.

The mechanism of the restoration of obliterated serial numbers by acid etching.

The mechanisms involved in the restoration of obliterated punch marks is discussed in relation to the chemistry and physics of steel.

A new trace ferrous metal detection reagent.

Since the early 1970s there has been substantial use of the 8-hydroxyquinoline test for determining whether a person has handled a weapon [1]. This test, now generally referred to as the TMDT test [2], involves spraying the hands of a person suspected of handling a weapon with a 0.2% solution of 8-hydroxyquinoline in isopropanol and observing the sprayed area with ultraviolet light. If a person has handled a weapon to the extent that oxidized ferrous ion is transferred to the hands, a dark area is noted in those areas of contact. Often a pattern of the object handled will be apparent. A positive reaction must be recorded by photography, however, and attendant complications exist in the ultraviolet fluorescent photography which must be employed [3].

The Examination of Cystolithic Hairs ot Cannabis and other Plants by means of the Scanning Electron Microscope

A number of plants similar in appearance to marijuana (Cannabis sativa) were examined using the scanning electron microscope. This information may be of assistance in identifying marijuana in routine investigations using the optical microscope.