Megan A. Ferguson
SUNY: New Paltz, Chemistry, Faculty Member
In the 2011 murder trial of Casey Anthony in Florida, the prosecution was permitted to introduce evidence regarding the chemical analysis of a carpet sample taken from the trunk of a Pontiac where the body of the victim, the two-year-old... more
In the 2011 murder trial of Casey Anthony in Florida, the prosecution was permitted to introduce evidence regarding the chemical analysis of a carpet sample taken from the trunk of a Pontiac where the body of the victim, the two-year-old daughter of the accused, may have been placed. The air from a Tedlar® bag that held the carpet sample was subjected to a series of steps, including cryotrapping and Gas Chromatography/Mass Spectrometry (GC/MS), resulting in the identification of 51 compounds, of which 41 were, according to the prosecution’s expert witness, consistent with a human decomposition event because they had been listed in a human decomposition database that he and research colleagues had prepared for the FBI. That database, however, has not been made public and was not released for consideration by the jury, the judge, or the defense expert witnesses at trial. Some of the 41 compounds were eliminated from consideration by the prosecution’s expert because such compounds are present in gasoline vapors, garbage and other items that either were or could have been in the trunk, leaving only 16 compounds consistent with a human decomposition event. This list was further reduced by comparison to a list of 30 compounds significant in human decomposition events, a list that appeared in a 2008 paper of which the prosecution’s expert was the lead author, leaving only 7 compounds, and 2 of these were eliminated because they were only present in trace levels. Thus, in the end, the prosecution’s expert based his argument that a body had been in the trunk on only 5 chemicals. Arguably additional chemicals could have been eliminated as not present in a positive control or as present at levels too high for a typical decomposition event. The trial judge denied a motion to exclude the evidence, finding that the technology used to isolate the 51 compounds with which the chemical analysis began had previously been held to satisfy scientific evidentiary standards. The judge failed, however, to consider whether the Frye standard for admission of scientific evidence should apply to any of the additional steps by which the original 51 chemicals were reduced to the 5 that the prosecution maintained were sufficient to indicate a decomposition event had occurred in the trunk of the car. This paper describes the chemical analysis used, the compounds reported to be associated with decomposition events in other studies, the trial judge’s ruling on the motion to exclude this evidence, and the history of the Frye and Daubert standards insofar as they have been applied to comparative and statistical steps in the presentation of scientific evidence. The authors conclude that the testimony of the prosecution’s expert witness should not have been admitted. However, the authors also conclude that continuing research is producing more and more information regarding the chemical profile of human decomposition and will most likely reach a level where such evidence can satisfy standards for admission in criminal trials.
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In the 2011 murder trial of Casey Anthony in Florida, the prosecution was permitted to introduce evidence regarding the chemical analysis of a carpet sample taken from the trunk of a Pontiac where the body of the victim, the two-year-old... more
In the 2011 murder trial of Casey Anthony in Florida, the prosecution was permitted to introduce evidence regarding the chemical analysis of a carpet sample taken from the trunk of a Pontiac where the body of the victim, the two-year-old daughter of the accused, may have been placed. The air from a Tedlar® bag that held the carpet sample was subjected to a series of steps, including cryotrapping and Gas Chromatography/Mass Spectrometry (GC/MS), resulting in the identification of 51 compounds, of which 41 were, according to the prosecution’s expert witness, consistent with a human decomposition event because they had been listed in a human decomposition database that he and research colleagues had prepared for the FBI. That database, however, has not been made public and was not released for consideration by the jury, the judge, or the defense expert witnesses at trial. Some of the 41 compounds were eliminated from consideration by the prosecution’s expert because such compounds are ...
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Predatory bacteria are an exciting area of investigation with great promise. Their impressive ability to devour other bacteria make them ideal candidates for clearing pathogens from the environment, water supply, and even the body.... more
Predatory bacteria are an exciting area of investigation with great promise. Their impressive ability to devour other bacteria make them ideal candidates for clearing pathogens from the environment, water supply, and even the body. However, scientists are still learning how these bacteria grow and consume their hosts. We are studying Bdellovibrio bacteriovorus, one of these predatory bacteria. We have been investigating the process of B. bacteriovorus attaching to prey cells of Escherichia coli in order to learn how they identify their prey, latch onto it, and then burrow into it. Measurements using atomic force microscopy (AFM) at different times during these processes have been made. Optical tweezers offer an alternative to the AFM for making measurements and learning about the attachment processes of B. bacteriovorus. Bacteria such as E. coli (1 – 2 µm long) and B. bacteriovorus (0.50 - 1 µm long) are a material and size that is easy to trap. Fluid solutions are the ideal medium for optical trapping measurements, and so it is readily possible to examine the bacteria during the attachment process. To this end, we trap one B. bacteriovorus cell in a single trap and move it close to a surface coated with E. coli, then move it away from the surface after increasingly long periods of time. This work shows preliminary measurements of attachment forces of predatory bacteria to their prey and correlates these measurements with those taken with the AFM.
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Bacterial biofilms have long been recognized as a source of persistent infections and industrial contamination with their intransigence generally attributed to their protective layer of extracellular polymeric substances (EPS). EPS,... more
Bacterial biofilms have long been recognized as a source of persistent infections and industrial contamination with their intransigence generally attributed to their protective layer of extracellular polymeric substances (EPS). EPS, consisting of secreted nucleic acids, proteins, and polysaccharides, make it difficult to fully eliminate biofilms by conventional chemical or physical means. Since most bacteria are capable of forming biofilms, understanding how biofilms respond to new antibiotic compounds and components of the immune system has important ramifications. Antimicrobial peptides (AMPs) are both potential novel antibiotic compounds and part of the immune response in many different organisms. Here, we use atomic force microscopy to investigate the biomechanical changes that occur in individual cells when a biofilm is exposed to the AMP magainin 2 (MAG2), which acts by permeabilizing bacterial membranes. While MAG2 is able to prevent biofilm initiation, cells in an establishe...
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Page 1. 3-1 Chapter 3 TIO2-PHOTOCATALYZED AS(III) OXIDATION IN AQUEOUS SUSPENSIONS: REACTION KINETICS AND EFFECTS OF ADSORPTION * Adapted from Ferguson et al., 2005. Environmental Science & Technology, vol. 39, no. 6, pp. 1880-1886.... more
Page 1. 3-1 Chapter 3 TIO2-PHOTOCATALYZED AS(III) OXIDATION IN AQUEOUS SUSPENSIONS: REACTION KINETICS AND EFFECTS OF ADSORPTION * Adapted from Ferguson et al., 2005. Environmental Science & Technology, vol. 39, no. 6, pp. 1880-1886. 3.1 ...
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Analytical techniques for measuring trace arsenic (As) concentrations, such as the method described in this article, have much lower detection limits than conventional As measurement methods, and broader adoption of such methods could... more
Analytical techniques for measuring trace arsenic (As) concentrations, such as the method described in this article, have much lower detection limits than conventional As measurement methods, and broader adoption of such methods could potentially drive a revision of the practical ...
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Compliance with the U.S. drinking water standard for arsenic (As) of 10 microg L(-1) is required in January 2006. This will necessitate implementation of treatment technologies for As removal by thousands of water suppliers. Although a... more
Compliance with the U.S. drinking water standard for arsenic (As) of 10 microg L(-1) is required in January 2006. This will necessitate implementation of treatment technologies for As removal by thousands of water suppliers. Although a variety of such technologies is available, most require preoxidation of As(III) to As(V) for efficient performance. Previous batch studies with illuminated TiO2 slurries have demonstrated that TiO2-photocatalyzed AS(III) oxidation occurs rapidly. This study examined reaction efficiency in a flow-through, fixed-bed reactor that provides a better model for treatment in practice. Glass beads were coated with mixed P25/sol gel TiO2 and employed in an upflow reactor irradiated from above. The reactor residence time, influent As(III) concentration, number of TiO2 coatings on the beads, solution matrix, and light source were varied to characterize this reaction and determine its feasibility for water treatment. Repeated usage of the same beads in multiple experiments or extended use was found to affect effluent As(V) concentrations but not the steady-state effluent As(III) concentration, which suggests that As(III) oxidation at the TiO2 surface undergoes dynamic sorption equilibration. Catalyst poisoning was not observed either from As(V) or from competitively adsorbing anions, although the higher steady-state effluent As(III) concentrations in synthetic groundwater compared to 5 mM NaNO3 indicated that competitive sorbates in the matrix partially hinder the reaction. A reactive transport model with rate constants proportional to incident light at each bead layer fit the experimental data well despite simplifying assumptions. TiO2-photocatalyzed oxidation of As(III) was also effective under natural sunlight. Limitations to the efficiency of As(III) oxidation in the fixed-bed reactor were attributable to constraints of the reactor geometry, which could be overcome by improved design. The fixed-bed TiO2 reactor offers an environmentally benign method for As(III) oxidation.
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Compliance with the U.S. drinking water standard for arsenic (As) of 10 microg L(-1) is required in January 2006. This will necessitate implementation of treatment technologies for As removal by thousands of water suppliers. Although a... more
Compliance with the U.S. drinking water standard for arsenic (As) of 10 microg L(-1) is required in January 2006. This will necessitate implementation of treatment technologies for As removal by thousands of water suppliers. Although a variety of such technologies is available, most require preoxidation of As(III) to As(V) for efficient performance. Previous batch studies with illuminated TiO2 slurries have demonstrated that TiO2-photocatalyzed AS(III) oxidation occurs rapidly. This study examined reaction efficiency in a flow-through, fixed-bed reactor that provides a better model for treatment in practice. Glass beads were coated with mixed P25/sol gel TiO2 and employed in an upflow reactor irradiated from above. The reactor residence time, influent As(III) concentration, number of TiO2 coatings on the beads, solution matrix, and light source were varied to characterize this reaction and determine its feasibility for water treatment. Repeated usage of the same beads in multiple experiments or extended use was found to affect effluent As(V) concentrations but not the steady-state effluent As(III) concentration, which suggests that As(III) oxidation at the TiO2 surface undergoes dynamic sorption equilibration. Catalyst poisoning was not observed either from As(V) or from competitively adsorbing anions, although the higher steady-state effluent As(III) concentrations in synthetic groundwater compared to 5 mM NaNO3 indicated that competitive sorbates in the matrix partially hinder the reaction. A reactive transport model with rate constants proportional to incident light at each bead layer fit the experimental data well despite simplifying assumptions. TiO2-photocatalyzed oxidation of As(III) was also effective under natural sunlight. Limitations to the efficiency of As(III) oxidation in the fixed-bed reactor were attributable to constraints of the reactor geometry, which could be overcome by improved design. The fixed-bed TiO2 reactor offers an environmentally benign method for As(III) oxidation.
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Analytical techniques for measuring trace arsenic (As) concentrations, such as the method described in this article, have much lower detection limits than conventional As measurement methods, and broader adoption of such methods could... more
Analytical techniques for measuring trace arsenic (As) concentrations, such as the method described in this article, have much lower detection limits than conventional As measurement methods, and broader adoption of such methods could potentially drive a revision of the practical ...
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... Megan A. Ferguson, Michael R. Hoffmann, and Janet G. Hering*. Department of Environmental Science and Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125. Environ. Sci. Technol.... more
... Megan A. Ferguson, Michael R. Hoffmann, and Janet G. Hering*. Department of Environmental Science and Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125. Environ. Sci. Technol. ...
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Bdellovibrio bacteriovorus 109J, a predatory bacterium with potential as a bacterial control agent, can exist in several lifestyles that differ both in predatory capacity and color. We determined that levels of ubiquinone-8 contribute to... more
Bdellovibrio bacteriovorus 109J, a predatory bacterium with potential as a bacterial control agent, can exist in several lifestyles that differ both in predatory capacity and color. We determined that levels of ubiquinone-8 contribute to the distinctive but variable yellow color of different types of Bdellovibrio cells. Steady-state ubiquinone-8 concentrations did not differ markedly between conventional predatory and host-independent B. bacteriovorus despite upregulation of a suite of ubiquinone-8 synthesis genes in host-independent cells. In contrast, in spatially organized B. bacteriovorus films, the yellow inner regions contain significantly higher ubiquinone-8 concentrations than the off-white outer regions. Correspondingly, RT-PCR analysis reveals that the inner region, previously shown to consist primarily of active predators, clearly expresses two ubiquinone biosynthesis genes, while the outer region, composed mainly of quiescent or stalled bdelloplasts, expresses those gene...
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Bdellovibrio bacteriovorus is a Gram-negative predator of other Gram-negative bacteria. Interestingly, Bdellovibrio bacteriovorus 109J cells grown in co-culture with Escherichia coli ML 35 prey develop into a spatially organized... more
Bdellovibrio bacteriovorus is a Gram-negative predator of other Gram-negative bacteria. Interestingly, Bdellovibrio bacteriovorus 109J cells grown in co-culture with Escherichia coli ML 35 prey develop into a spatially organized two-dimensional film when located on a nutrient-rich surface. From deposition of 10 μL of a routine cleared co-culture of B. bacteriovorus and E. coli cells, the cells multiply into a macroscopic community and segregate into an inner, yellow colored circular region and an outer, off-white colored region. Fluorescence in situ hybridization and atomic force microscopy measurements confirm that the mature film is spatially organized into two morphologically distinct Bdellovibrio populations, with primarily small, vibroid cells in the center and a complex mixture of pleiomorphic cells in the outer radii. The interior region cell population exhibit the hunting phenotype while the outer region cell sub-population does not. Crowding and high nutrient availability w...
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... Megan A. Ferguson, Michael R. Hoffmann, and Janet G. Hering*. Department of Environmental Science and Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125. Environ. Sci. Technol.... more
... Megan A. Ferguson, Michael R. Hoffmann, and Janet G. Hering*. Department of Environmental Science and Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125. Environ. Sci. Technol. ...
Research Interests:
Atomic force microscopy offers a way to probe physical properties of bacteria that are adhered to a surface. We study early stage biofilms that natively adhere to a glass surface, without artificial fixation methods. We present images and... more
Atomic force microscopy offers a way to probe physical properties of bacteria that are adhered to a surface. We study early stage biofilms that natively adhere to a glass surface, without artificial fixation methods. We present images and force curves from five different bacteria, ...