Bayes\u27 Law, Sequential Uncertainties, and Evidence of Causation in Toxic Tort Cases

Judges are the gatekeepers of evidence. Arguably, the most difficult duty for a judicial gatekeeper is to screen the reliability of expert opinions in scientific fields such as medicine that are beyond the ken of most judges. Yet, judges have a duty to scrutinize such expert opinion evidence to determine its reliability and admissibility. In toxic tort cases, the issue of causation-whether the alleged exposures actually caused the plaintiffs injury-is nearly always the central dispute, and determining admissibility of expert causation opinion is a daunting challenge for most judges. We present a comprehensive review of the courts\u27 struggles with the screening of scientific evidence in such cases. In addition, we propose an approach to the screening of causation opinions based on probability science and logic. Central to this approach is Bayes\u27 Law, a statistical tool that courts can use to analyze the extrinsic reliability of proffered causation testimony. We explain Bayes\u27 Law and illustrate its potential application for evaluating the reliability of medical and scientific causation testimony. All evidence is probabilistic. There are uncertainties attending all testimony, not only because the honesty or objectivity of witnesses may be doubtful, but also because even honest and unbiased witnesses may be mistaken in their perceptions. Reliability of causation evidence depends on both sensitivity and specificity of the tests used to determine causation. Highly sensitive tests of causation reflect an ability to identify a high percentage of those with the agent-induced disease, whereas highly specific tests of causation reflect an ability to reject a high percentage of those who have the disease, but not induced by the agent at issue. According to Bayes\u27 Law, the reliability of causation opinion depends not only on the sensitivity and specificity of the tests employed by the causation expert, but also on the base rate of the agent-induced disease in the population. Bayes\u27 Law dictates that the lower the rate of the agent-induced disease in the population, the less reliable the opinion that the agent at issue in fact caused the plaintiffs disease given certain levels of sensitivity and specificity. The base-rate problem and its effect on reliability of causation opinions are overlooked by judges when scrutinizing the reliability of proffered causation evidence. In this Article, we encourage courts to consider a Bayes\u27 Law approach to screen out, at an early stage, those claims of injury lacking reliable evidence that an injury was more likely than not caused by exposures to toxic agents. The goal of our Article is to provide a framework that helps the gatekeeper to screen out toxic tort claims insufficiently substantiated by the underlying scientific and medical data, and allow the factfinder to decide only those toxic tort claims for which there is reliable and relevant scientific support for each link of the causal chain, from subject exposure to the injury Scientific substantiation of each causal link determines the reliability of an experts opinion that the exposure more likely than not caused the plaintiffs injury

Nonlinear summation of M- and L-cone inputs to phasic retinal ganglion cells of the macaque.

We have studied the responses of ganglion cells in the macaque retina to stimuli that alternate in color. With most color combinations, the phasic retinal ganglion cells, which sum input from M- and L-cones in both center and surround, showed a response with twice the alternation frequency at equal luminance. This frequency doubling was directly related to the degree to which the M- and L-cones were stimulated out- of-phase with one another, and thus varied with the wavelength combinations used. It was absent with wavelength combinations that lay along tritanopic confusion lines, when at equal luminance the M- and L- cones are not modulated. Such a frequency-doubled response is evidence for a nonlinearity at or before M- and L-cone summation. The effect became much smaller or was abolished when the receptive field center alone was stimulated, indicating that its mechanism lies in the surround or in a center-surround interaction. Also, it was much more marked at high luminance levels, being almost absent at retinal illuminances below 100 td. Its origin is not clear, but it seems to derive more from the L- than the M-cone. The results imply that phasic cells, through this nonlinearity, could respond to the red-green equal luminance borders used in some psychophysical experiments

Comment on the Nanoparticle Conclusions in Crüts et al. (2008), "Exposure to diesel exhaust induces changes in EEG in human volunteers"

A recent publication in this journal reported interesting changes in electroencephalographic (EEG) waves that occurred in 10 young, male volunteers following inhalation for one hour of elevated levels of diesel-engine exhaust fumes [1]. The authors then proposed a chain of causal events that they hypothesized underlay their observed EEG changes. Their reasoning linked the observed results to nanoparticles in diesel-engine exhaust (DEE), and went on to suggest that associations between changes in ambient particulate matter (PM) levels and changes in health statistics might be due to the effects of diesel-engine exhaust (DEE) nanoparticles on EEG. We suggest that the extrapolations of the Crüts et al. EEG findings to casual mechanisms about how ambient levels of DEE particulate might affect electrical signals in the brain, and subsequently to how DEE particulate might alter disease risk, are premature

Workgroup Report: Base Stations and Wireless Networks—Radiofrequency (RF) Exposures and Health Consequences

Radiofrequency (RF) waves have long been used for different types of information exchange via the airwaves—wireless Morse code, radio, television, and wireless telephony (i.e., construction and operation of telephones or telephonic systems). Increasingly larger numbers of people rely on mobile telephone technology, and health concerns about the associated RF exposure have been raised, particularly because the mobile phone handset operates in close proximity to the human body, and also because large numbers of base station antennas are required to provide widespread availability of service to large populations. The World Health Organization convened an expert workshop to discuss the current state of cellular-telephone health issues, and this article brings together several of the key points that were addressed. The possibility of RF health effects has been investigated in epidemiology studies of cellular telephone users and workers in RF occupations, in experiments with animals exposed to cell-phone RF, and via biophysical consideration of cell-phone RF electric-field intensity and the effect of RF modulation schemes. As summarized here, these separate avenues of scientific investigation provide little support for adverse health effects arising from RF exposure at levels below current international standards. Moreover, radio and television broadcast waves have exposed populations to RF for > 50 years with little evidence of deleterious health consequences. Despite unavoidable uncertainty, current scientific data are consistent with the conclusion that public exposures to permissible RF levels from mobile telephony and base stations are not likely to adversely affect human health

Microrheology, stress fluctuations and active behavior of living cells

We report the first measurements of the intrinsic strain fluctuations of living cells using a recently-developed tracer correlation technique along with a theoretical framework for interpreting such data in heterogeneous media with non-thermal driving. The fluctuations' spatial and temporal correlations indicate that the cytoskeleton can be treated as a course-grained continuum with power-law rheology, driven by a spatially random stress tensor field. Combined with recent cell rheology results, our data imply that intracellular stress fluctuations have a nearly $1/\omega^2$ power spectrum, as expected for a continuum with a slowly evolving internal prestress.Comment: 4 pages, 2 figures, to appear in Phys. Rev. Let

Impact of alpha-tocopherol deficiency and supplementation on sacrocaudalis and gluteal muscle fiber histopathology and morphology in horses.

BackgroundA subset of horses deficient in alpha-tocopherol (α-TP) develop muscle atrophy and vitamin E-responsive myopathy (VEM) characterized by mitochondrial alterations in the sacrocaudalis dorsalis medialis muscle (SC).ObjectivesTo quantify muscle histopathologic abnormalities in subclinical α-TP deficient horses before and after α-TP supplementation and compare with retrospective (r)VEM cases.AnimalsProspective study; 16 healthy α-TP-deficient Quarter Horses. Retrospective study; 10 retrospective vitamin E-responsive myopathy (rVEM) cases .MethodsBlood, SC, and gluteus medius (GM) biopsy specimens were obtained before (day 0) and 56 days after 5000 IU/450 kg horse/day PO water dispersible liquid α-TP (n = 8) or control (n = 8). Muscle fiber morphology and mitochondrial alterations were compared in samples from days 0 and 56 and in rVEM cases.ResultsMitochondrial alterations more common than our reference range (<2.5% affected fibers) were present in 3/8 control and 4/8 treatment horses on day 0 in SC but not in GM (mean, 2.2; range, 0%-10% of fibers). Supplementation with α-TP for 56 days did not change the percentage of fibers with mitochondrial alterations or anguloid atrophy, or fiber size in GM or SC. Clinical rVEM horses had significantly more mitochondrial alterations (rVEM SC, 13% ± 7%; GM, 3% ± 2%) and anguloid atrophy compared to subclinical day 0 horses.Conclusions and clinical importanceClinically normal α-TP-deficient horses can have mitochondrial alterations in the SC that are less severe than in atrophied VEM cases and do not resolve after 56 days of α-TP supplementation. Preventing α-TP deficiency may be of long-term importance for mitochondrial viability