Lessons learned from inter-laboratory studies of carbon isotope analysis of honey

Forensic application of carbon isotope ratio measurements of honey and honey protein to investigate the degree of adulteration with high fructose corn syrup or other C₄ plant sugars is well established. These measurements must use methods that exhibit suitable performance criteria, particularly with regard to measurement uncertainty and traceability – low levels of adulteration can only be detected by methods that result in suitably small measurement uncertainties such that differences of 1‰ or less can be reliably detected. Inter-laboratory exercises are invaluable to assess the state-of-the art of measurement capabilities of laboratories necessary to achieve such performance criteria. National and designated metrology institutes from a number of countries recently participated in an inter-laboratory assessment (CCQM-K140) of stable carbon isotope ratio determination of bulk honey. The same sample material was distributed to a number of forensic isotope analysis laboratories that could not participate directly in the metrological comparison. The results from these studies have demonstrated that the majority of participants provided isotope delta values with acceptable performance metrics; that all participants ensured traceability of their results; and that where measurement uncertainties were reported; these were fit-for-purpose. A number of the forensic laboratories only reported precision rather than full estimates of measurement uncertainty and this was the major cause of the few instances of questionable performance metrics. Reporting of standard deviations in place of measurement uncertainties is common practice outside metrology institutes and the implications for interpretations of small differences in isotopic compositions are discussed. The results have also highlighted a number of considerations that are useful for organisers of similar inter-laboratory studies in the future.     

Preliminary Studies on the Absorbance Ratio Method Used to Determining the Age of Stamp‐pad Ink Seal

Stamp‐pad ink seals are often placed on important documents, and determining the dating of stamp‐pad ink seal is important to assess the authenticity of a document. In this study, 20 different brands and types of stamp‐pad inks were classified by ultraviolet visible spectrophotometer. Six different brands and types of papers were classified by micro‐Fourier transform infrared spectrometer and visual spectral comparator 6000. Three different brands of stamp‐pad inks and two different types of paper were used to make diachronic samples of the seals. A method was employed to date the stamp‐pad seals by comparing absorbance ratios and inks of known age. Curves were created to show the relationship between the absorbance ratio of ink and the age of the seals. The experimental results showed that the absorbance ratio method was applicable for the relative dating of stamp‐pad ink seals in some cases where the seal was placed on the document within 10 weeks.     

Traveling There and Back Again: A Fingernail's Tale

This study focuses on the examination of stable isotope biomarkers in human fingernails of travelers who ventured away from Salt Lake City, UT and subsequently returned. Here, we describe three case studies examining: individual travelers (n = 4), paired travelers (n = 2), and a traveler (n = 1) who repeatedly left and returned. Our case studies examined the influences of dietary and drinking water inputs on fingernail stable isotope profiles for reconstructing travel histories. Stable isotope data were compared with theoretical and predictive models that laid the groundwork for anthropological and forensic geospatial reconstruction of travel histories. Drinking water inputs strongly influenced stable isotope profiles and the patterns observed were consistent with reported travel histories. Finally, observed fingernail stable isotope ratio data were consistent with modeled rates of stable isotope turnover and transition to expected values for the new environment. The results of our study further support the use of fingernail tissues for travel history reconstruction.     

Ink dating part II: Interpretation of results in a legal perspective

The development of an ink dating method requires an important investment of resources in order to step from the monitoring of ink ageing on paper to the determination of the actual age of a questioned ink entry. This article aimed at developing and evaluating the potential of three interpretation models to date ink entries in a legal perspective: (1) the threshold model comparing analytical results to tabulated values in order to determine the maximal possible age of an ink entry, (2) the trend tests that focusing on the “ageing status” of an ink entry, and (3) the likelihood ratio calculation comparing the probabilities to observe the results under at least two alternative hypotheses. This is the first report showing ink dating interpretation results on a ballpoint be ink reference population.In the first part of this paper three ageing parameters were selected as promising from the population of 25 ink entries aged during 4 to 304 days: the quantity of phenoxyethanol (PE), the difference between the PE quantities contained in a naturally aged sample and an artificially aged sample (R_NORM) and the solvent loss ratio (R%). In the current part, each model was tested using the three selected ageing parameters. Results showed that threshold definition remains a simple model easily applicable in practice, but that the risk of false positive cannot be completely avoided without reducing significantly the feasibility of the ink dating approaches. The trend tests from the literature showed unreliable results and an alternative had to be developed yielding encouraging results. The likelihood ratio calculation introduced a degree of certainty to the ink dating conclusion in comparison to the threshold approach. The proposed model remains quite simple to apply in practice, but should be further developed in order to yield reliable results in practice.     

Profiling the scent of weathered training aids for blood-detection dogs

At outdoor crime scenes, cadaver-detection and blood-detection dogs may be tasked with locating blood that is days, weeks or months old. Although it is known that the odour profile of blood will change during this time, it is currently unknown how the profile changes when exposed to the environment. Such variables must be studied in order to understand when the odour profile is no longer detectable by the scent-detection dogs and other crime scene tools should be implemented. In this study, blood was deposited onto concrete and varnished wood surfaces and weathered in an outdoor environment over a three-month period. Headspace samples were collected using solid phase microextraction (SPME) and analysed using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GC×GC–TOFMS). The chemical odour profiles were compared with the behavioural responses of cadaver-detection and blood-detection dogs during training. Data interpretation using principal component analysis (PCA) and hierarchical cluster analysis (HCA) established that the blood odour could no longer be detected using SPME–GC×GC–TOFMS after two months of weathering on both surfaces. Conversely, the blood-detection dogs had difficulty locating the blood samples after one month of weathering on concrete and after one week of weathering on varnished wood. The scent-detection dogs evaluated herein had not been previously exposed to environmentally weathered blood samples during training. Given that this study was conducted to test the dogs' baseline abilities, it is expected that with repeated exposure, the dogs' capabilities would likely improve. The knowledge gained from this study can assist in providing law enforcement with more accurate training aids for blood-detection dogs and can improve their efficiency when deployed to outdoor crime scenes.     

Reflections on variability in the blood–breath ratio of ethanol and its importance when evidential breath-alcohol instruments are used in law enforcement

Variability in the blood–breath ratio (BBR) of alcohol is important, because it relates a measurement of the blood-alcohol concentration (BAC) with the co-existing breath-alcohol concentration (BrAC). The BBR is also used to establish the statutory BrAC limit for driving from the existing statutory BAC limits in different countries. The in-vivo BBR depends on a host of analytical, sampling and physiological factors, including subject demographics, time after end of drinking (rising or falling BAC), the nature of the blood draw (whether venous or arterial) and the subject’s breathing pattern prior to exhalation into the breath analyzer. The results from a controlled drinking study involving healthy volunteers (85 men and 15 women) from three ethnic groups (Caucasians, Hispanics and African Americans) were used to evaluate various factors influencing the BBR. Ethanol in breath was determined with a quantitative infrared analyzer (Intoxilyzer 8000) and BAC was determined by headspace gas chromatography (HS-GC). The BAC and BrAC were highly correlated (r = 0.948) and the BBR in the post-absorptive state was 2 382 ± 119 (mean ± SD). The BBR did not depend on gender (female: 2 396 ± 101 and male: 2 380 ± 123, P > 0.05) nor on racial group (Caucasians 2 398 ± 124, African Americans 2 344 ± 119 and Hispanics 2 364 ± 104, P > 0.05). The BBR was lower in subjects with higher breath- and body-temperatures (P < 0.05) and it also decreased with longer exhalation times into the breath-analyzer (P < 0.001). In the post-absorptive state, none of the 100 subjects had a BBR of less than 2 100:1.     

中国县区级出生性别比治理的社会政策系统协调性分析

本研究采用政策系统协调性分析框架,对中国县区级出生性别比治理的社会政策系统协调性进行分析,揭示了目前县区级出生性别比治理相关社会政策系统中所存在的不协调问题。其中,系统内部不协调主要包括政策主体内部的不协调、政策客体内部的不协调以及主体和客体之间的不协调;系统外部不协调主要包括本社会政策系统与其他政策系统之间的不协调,以及本政策系统与环境之间的不协调。     

A response to Busey & Klutzke (2022): Regarding subjective assignment of likelihood ratios

Busey & Klutzke (2022) states that “Morrison (2012) has argued that the likelihood ratio need not be quantitative but could be based on the expert’s subjective evaluation.” The statement appears to suggest that Morrison (2012) argued in favour of subjective assignment of likelihood-ratio values. This interpretation of Morrison (2012) is incorrect.