Computational design of a self-assembling ß-peptide oligomer.

The first computationally designed self-assembling oligomer consisting of exclusively ß-amino acids (ßAAs) is presented. The packing of a ß-3(14) helix into coiled-coils of varying stoichiometries as a function of amino acid sequence is examined. ß-Peptides with hVal repeating every third residue in the sequence appeared to have a strong propensity to pack into hexameric bundles. The designed sequence was synthesized and characterized with CD spectroscopy, NMR, and analytical ultracentrifugation, suggesting that the peptide adopts a well-folded hexameric structure.

Thirty-site P300 scalp distribution, amplitude variance across sites, and amplitude in detection of deceptive concealment of multiple guilty items.

Previous tests of P300 in deception detection have focused mainly on amplitude analysis. Since countermeasures for such tests have been reported, we looked here at other possible variables as deception indices: P300 scalp distribution and amplitude variance, both across 30 sites. We were also concerned, for the first time, in testing for recognition of more than one guilty item in a mock crime scenario. There were three groups: (1) two-probe group, two of six items were guilty knowledge (GK) items; (2) three-probe group, three of six items were GK items; (3) control group, zero of six items were GK items. In group analyses, in the two-probe group, P300s for lies were significantly greater than P300s for truthful responses. There were significant interactions of condition (Lie vs Truth) by site, suggesting different scalp profiles for deceptive versus truthful responding. Amplitude variance across sites was also greater in Lie than in Truth blocks. These results did not obtain in the three-probe and control groups. In terms of amplitude variances in probe conditions across groups, two-probe group was larger than three-probe and control groups. Regarding individual diagnostics, the variance method yielded a greater-than-chance detection rate of 71% versus 28% false positives. Regarding amplitude at multiple nonfrontal sites, 71% of guilty subjects were detected versus 14% false positives. Grier's (1971) A' indices of various test discrimination efficiencies varied from .76 to .87. Results of the present study suggested further investigation of the variance method as a diagnostic tool for lie detection.

Facial skin surface temperature changes during a "concealed information" test.

When individuals who commit a crime are questioned, they often show involuntary physiological responses to remembered details of that crime. This phenomenon is the basis for the concealed information test, in which rarely occurring crime-related details are embedded in a series of more frequently occurring crime-irrelevant items while respiratory, cardiovascular, and electrodermal responses are recorded. Two experiments were completed to investigate the feasibility of using facial skin surface temperature (SST) measures recorded using high definition thermographic images as the physiological measure during a concealed information test. Participants were randomly assigned to nondeceptive or deceptive groups. Deceptive participants completed a mock-crime paradigm. A focal plane array thermal imaging radiometer was used to monitor SST while crime-relevant and crime-irrelevant items were verbally presented to each participant. During both experiments, there were significant facial SST differences between deceptive and nondeceptive participants early in the analysis interval. In the second experiment, hemifacial (i.e., "half-face" divided along the longitudinal axis) effects were combined with the bilateral responses to correctly classify 91.7% of participants. These results suggest that thermal image analysis can be effective in discriminating deceptive and nondeceptive individuals during a concealed information test.

Comparison of polygraph data obtained from individuals involved in mock crimes and actual criminal investigations.

In a preliminary attempt to determine the generalizability of data from laboratory mock-crime studies, the authors examined the similarities and differences among the cardiovascular, electrodermal, and respiration responses of deceptive and nondeceptive individuals elicited to crime-relevant and crime-irrelevant questions. Participants in the laboratory group were randomly assigned to nondeceptive (n = 28) or deceptive (n = 27) treatment groups, and a mock-crime scenario was used. The field participants were confirmed nondeceptive (n = 28) or deceptive (n = 39) criminal suspects who underwent polygraph examinations between 1993 and 1997. The results indicated that there were salient differences between field and similarly obtained laboratory polygraph response measures. However, accuracy of laboratory participants' classifications using logistic regression analysis was not significantly different from field participants' classification accuracy.