John I. Thornton’s research while affiliated with University of California, Berkeley and other places

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Publications (43)


A Review of Hung Jury: The Diary of a Menendez Juror
  • Article

September 1996

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14 Reads

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1 Citation

Journal of Forensic Sciences

John I. Thornton

I have never met Hazel Thornton, although in the past few months, I have spoken to her on the phone a couple of times. We share the same last name, and apparently, the same great great grandfather. But until very recently, we were oblivious to each other's existence.



Firearm cartridge case comparison by graphite furnace atomic absorption spectrochemical determination of nickel, iron and lead

March 1994

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12 Reads

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3 Citations

Analytica Chimica Acta

Graphite furnace atomic absorption spectrometry was used to determine the concentrations of nickel, iron, and lead in 26 different production lots of Winchester-Western cartridge case brass. In most cases, the measured elemental concentrations were found to be normally distributed within a lot, and the variables lacked any strong association. It was found that the concentrations of these three elements could be used as a basis for the comparison of individual cartridge cases to determine their provenance. Using the T-test with a significance level of 0.01, the frequency of obtaining a ‘true match’ and a ‘false match’ were found to be 98.1% and 0.43%, respectively. Additionally, a likelihood ratio was used to evaluate the extent to which provenance, or “common origin” among brass cartridge cases can be established.


The chemistry of death by gunshot

March 1994

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80 Reads

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34 Citations

Analytica Chimica Acta

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.


Characterization of smokeless gunpowder by means of diphenylamine stabilizer and its nitrate derivatives

March 1994

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80 Reads

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54 Citations

Analytica Chimica Acta

Smokeless gunpowder frequently contains diphenylamine as a stabilizer. The diphenylamine acts as a nitrate scavenger and in turn is nitrated by complex processes. The various nitrated congeners of diphenylamine, which are numerous, may serve to characterize a sample of gunpowder because these derivatives reflect not only the production of the gunpowder, but also its storage' career and thermal history following manufacture. These derivatives of diphenylamine may be isolated and identified by means of thin-layer chromatography and liquid chromatography.


Reduction of Specular Reflectance on Projectiles and Toolmarks by Ammonium Chloride Fuming

July 1993

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2 Reads

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3 Citations

Journal of Forensic Sciences

A method for reducing specular reflectance from metallic surfaces in which ammonium chloride is used as a fuming reagent is described. This method has the advantage of being easily controlled, and is rapid. The deposit of ammonium chloride salt on the metallic surface is easily and effectively removed by washing.


The Use of k Values in the Interpretation of Glass Density and Refractive Index Data

November 1989

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4 Reads

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8 Citations

Journal of Forensic Sciences

A κ value represents a type of summary statistic by means of which glass evidence may be interpreted. This statistic is defined as κ = V/D, where the dispersion V = (n(D) - 1)/(n(F) - n(C)), and where D is the density. The κ value is therefore the slope of a line through the 0,0 origin and a plot of dispersion versus density. Obtaining a κ value facilitates the interpretation of commonality of source, since 'within-item' variation in density and refractive index does not significantly alter the κ value. 'Between-item' variation, on the other hand, profoundly influences the κ value, even if the density and one of the refractive indices are coincidentally similar.


A Trajectory Analysis of Billy Dixon's Long Shot

July 1989

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8 Reads

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1 Citation

Journal of Forensic Sciences

At the Second Battle of Adobe Walls, in June 1874, Billy Dixon shot an Indian at a range of 1538 yd, give or take just a few. A computer analysis of this trajectory indicates that the bullet drop would have been 3823.8 in., the time of flight 4.838 s, and the windage adjustment would have been 337.8 in.


Multivariate Analysis of Typeface Damage Frequencies

May 1989

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1 Read

Journal of Forensic Sciences

To explore possible deterministic factors in typeface damage, multivariate analysis was performed on data developed by Dr. David Crown in his doctoral dissertation on typewriter individuality. Crown observed a slow increase in collective typeface damage with the duration of typewriter use, but found no apparent increase in damage correlated with individual letter use frequencies. These findings seemed peculiar and were the initial motivation for the present study. For multivariate analysis, three groups of dependent variables were defined: those based on letter use frequencies; those based on letter form; and those based on basket or keyboard position. Both letter-use frequency and letter area showed statistically significant positive correlation with typeface damage frequencies. Together, these two variables accounted for 42% of the observed variation in damage frequencies. None of the other variables tested was able to explain any statistically significant portion of the remaining variation. These variables included use frequencies associated with difficult finger movements, vertical extension of letters, basket position, and keyboard row. The 58% residual variation must be combined with additional variation introduced by the form and position of typeface damage. With this amount of variation left unexplained, the deterministic factors identified in this study are of little significance in the interpretation of typewriting comparisons.


Fluorescence In Blood Stain Detection

April 1988

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9 Reads

Proceedings of SPIE - The International Society for Optical Engineering

Two fluorescent probes, ANS and TNS, have been further examined for their effectiveness in acting as fluorescent probes for the detection of blood stain patterns. These materials, which are not fluorescent in aqueous solution, react non-specifically with protein and enable an observer to discern a blood pattern when viewed under UV light at 365 nm. Other possible fluorescent probes have been evaluated and rejected for various reasons; these include luminol, tetramethylbenzidine, p-hvdroxy-phenylacetic acid, 3,4-dihydroxyphenylacetic acid, and 2,7-aminofluorene.


Citations (24)


... Further discrimination may be achieved by the comparison of the chemical composition of the topcoats. The chemistry of paint can be determined using microchemical spot tests (7,8), infrared spectroscopy (1)(2)(3), elemental analysis (9,10), and pyrolysis-gas chromatography (11)(12)(13). ...

Reference:

Comparison and Identification of Automotive Topcoats: Microchemical Spot Tests, Microspectrophotometry, Pyrolysis-Gas Chromatography, and Diamond Anvil Cell Ftir
Solubility Characterization of Automotive Paints
  • Citing Article
  • October 1983

Journal of Forensic Sciences

... Dear Sir: In reply to Dr. Sperber's letter, I refer to page 1239 of the article under discussion [1]. The authors describe a bite mark impression technique in which impression material sets completely, is covered with orthopedic tape and then with another layer of impression material. ...

A Trajectory Analysis of Billy Dixon's Long Shot
  • Citing Article
  • July 1989

Journal of Forensic Sciences

... Because of the cost and complexity of many of the examinations, the results of each analysis (e.g., refractive index of the suspect fragment and the possible source) should be compared before proceeding to the next test. Some properties and characteristics of glass to be considered are the shape (physical match or jig-saw fit); surface features, such as flatness and fracturing (9,14,21,24); color; density (5,12,16,20,28,36,38,39); refractive index (3,4,7,8,(10)(11)(12)(13)15,17,22,27,32,36,38,39,43); elemental composition (2,6,18,19,23,33); and dispersion properties (13,15,36). ...

Estimation of the Absolute Density of Glass Following the Sink/Float Technique
  • Citing Article
  • January 1987

Journal of Forensic Sciences

... Because of the cost and complexity of many of the examinations, the results of each analysis (e.g., refractive index of the suspect fragment and the possible source) should be compared before proceeding to the next test. Some properties and characteristics of glass to be considered are the shape (physical match or jig-saw fit); surface features, such as flatness and fracturing (9,14,21,24); color; density (5,12,16,20,28,36,38,39); refractive index (3,4,7,8,(10)(11)(12)(13)15,17,22,27,32,36,38,39,43); elemental composition (2,6,18,19,23,33); and dispersion properties (13,15,36). ...

Three-Dimensional Presentation of Glass Density Versus Refractive Index Data
  • Citing Article
  • April 1986

Journal of Forensic Sciences

... However, it has a slight fluctuation for the films with As content around 38.0 %. It is well known that, thermal annealing can induce the change of the material density [20]. The decrease in density is reflected by the increase in film thickness, leading to a decrease of the refractive index. ...

Correlation of Glass Density and Refractive Index—Implications to Density Gradient Construction
  • Citing Article
  • July 1984

Journal of Forensic Sciences

... The first research direction is based on quantifying the value of the evidence based on the frequencies of occurrence of fingerprint features [4][5][6]. The second research direction is based on quantifying the evidential strength of a similarity score generated by an algorithm [7][8][9][10][11]. ...

A Systematic Study of Epidermal Ridge Minutiae
  • Citing Article
  • September 1987

Journal of Forensic Sciences

... remember that all strain modes-tension, compression, and shear-act simultaneously to produce a bone fracture. Fracture morphology is attributed to a complex interaction of tension, compression, and shear forces that can be loaded in a quasi-static (slow) or dynamic (rapid) manner (L'Abbé et al. 2015(L'Abbé et al. , 2019Symes et al. 2012; Thornton and Cashman 1986). ...

Glass fracture mechanism - a rethinking
  • Citing Article
  • July 1986

Journal of Forensic Sciences

... Forensic analysis of glass has typically been based on refractive index, dispersion and density analyses. 76 In 1991, the statistical discrimination of flat glass by neutron activation analysis of the sample's elemental composition was demonstrated. 77 The determination of up to 70 elements by ICP-MS was later demonstrated. ...

The Use of k Values in the Interpretation of Glass Density and Refractive Index Data
  • Citing Article
  • November 1989

Journal of Forensic Sciences

... So far dithizone, zincon and chlorindazone DS have been tested for effectiveness. Dithizone [4,5] is a method that could be applied when the items of evidence are exclusively treated in a forensic science laboratory. It was necessary Volume 35, Number 2 to transfer the GSR from the targeted object onto photo paper as secondary matrix in order to guarantee a reproducible visualization. ...

Dithizone as a Microcrystalline Test for the Confirmation of Projectile Lead Wipes
  • Citing Article
  • January 1987

Journal of Forensic Sciences

... Several authors across the globe (Gutiérrez-Redomero et al. 2011;Adamu et al. 2017;Akpan et al. 2019) documented great variations in terms of fingerprint minutiae in different areas of finger as well as in different population. A study conducted by Stoney and Thornton (1986) also highlighted direct significance of the variations of epidermal ridge minutiae in the forensic science and criminal investigations for analyzing and comparing different fingerprints especially in case of partial fingerprints. Another interesting finding of Wilder and Wentworth (1918) noted that the frequency of minutiae depends on the type of dermatoglyphic pattern of the individual, with high frequency of minutiae are recorded in the loops as well as in the delta region. ...

A Method for the Description of Minutia Pairs in Epidermal Ridge Patterns
  • Citing Article
  • October 1986

Journal of Forensic Sciences