Development and usage of a NIST standard reference material for real time PCR quantitation of human DNA

National Institute of Standards and Technology SRM 2372 human DNA quantitation standard has been produced to support the need for a human-specific DNA quantitation standard in forensic casework and calibration of new quantitative polymerase chain reaction (qPCR) assays. The conventional DNA concentration has been assigned with one of the U.S. National Reference UV/Visible Spectrophotometers, assuming an absorbance of 1.0 at 260 nm equals 50 ng/μL of double stranded DNA. In addition, an interlaboratory study has been conducted, to verify that the SRM 2372 materials perform well in currently used DNA quantitation assays by the forensic DNA community. Each unit of SRM 2372 consists of three well-characterized DNA extracts. Component A is a single-source human male material derived from blood. Component B is a multiple-source human female material derived from blood. Component C was purchased as a purified unsheared genomic human DNA (Sigma-Aldrich Co., St. Louis, MO) obtained as a lyophilized human genomic extract and has both male and female donors. SRM 2372 is intended to enable the comparison of DNA concentration measurements across time and place. Manufacturers can use SRM 2372 to validate the values assigned to their own reference materials. Individual forensic laboratories can use SRM 2372 to validate DNA quantitation methods and to verify the assigned concentration of in-house or commercial DNA calibration standards.     

Is there a magical time boundary for diagnosing eyewitness identification accuracy in sequential line‐ups?

We examined whether eyewitness identification latencies for sequential line‐up decisions indicate an optimum time boundary that reliably discriminates accurate from inaccurate decisions. Participants (N = 381) observed a crime simulation and attempted two separate identifications from target‐present or target‐absent sequential line‐ups. As has previously been found with simultaneous line‐ups, the optimum time boundary identified did not reliably discriminate accurate from inaccurate identifications for both line‐up targets. Diagnosticity for choosers was, however, much higher at very high confidence levels than at lower levels. Possible reasons for why one index of signal strength (confidence), but not another (latency), might postdict accuracy within the sequential framework were presented.     

Command of the Sea with Chinese Characteristics

As globalization accelerates, U.S. foreign policy makers have become less convinced of the influence geopolitics and power politics have on international affairs. They now risk losing touch with rising competitors like China that continue to view the international system in geopolitical terms. Chinese geopolitical strategists have great influence with the country's defense policy makers, who are focusing increasingly on the need for China to establish command of the seas—a goal that threatens conflict between it and the United States throughout Asia. In order to prevent a return to a world dominated by aggressive, geopolitically driven actors, the United States cannot afford to assume that China shares its worldview and that geopolitics has disappeared from international relations.     

An investigation into the use of calculating the first derivative of absorbance spectra as a tool for forensic fibre analysis.

A range of fibre samples was measured using J&M MSP400 and J&M MSP800 microspectrophotometers across the visible and UV/visible wavelength ranges respectively. The first derivative of the absorbance spectra was then calculated and studied. When the absorbance spectra produced for some samples were broad and featureless, the first derivative spectra provided more points of comparison that facilitated discrimination. For many of the samples, calculating the first derivative did not result in any additional discrimination due to the high number of points of comparison present in the absorbance spectra. However, for the samples that exhibited a high level of intra-sample colour variation (e.g. through uneven dye uptake common in cotton and wool, etc.), which was evident in the absorbance spectra, the associated first derivative spectra highlighted this variation between the fibres and could potentially have resulted in false exclusions. The results show that whilst calculating first derivative can be a useful aid in the comparison of spectra, a high degree of caution is required when applying this method to fibres which exhibit a large intra-sample variation in colour.