The Downstream Benefits of Experimentation

The debate about the cost-effectiveness of randomized fieldexperimentation ignores one of the most important potentialuses of experimental data. This article defines and illustrates"downstream" experimental analysis—that is, analysis ofthe indirect effects of experimental interventions. We arguethat downstream analysis may be as valuable as conventionalanalysis, perhaps even more so in the case of laboratory experimentation.     

The use of SEM/EDS analysis to distinguish dental and osseus tissue from other materials

With increasing frequency, relatively small, fragmentary evidence thought to be osseous or dental tissue of human origin is submitted to the forensic laboratory for DNA analysis with the request for positive identification. Prior to performing DNA analysis, however, it is prudent to first perform a presumptive test or "screen" to determine whether the questioned material may be eliminated from further consideration. When material is shown not to be consistent with bone/teeth, DNA testing is not performed. When such determinations cannot be made from gross morphological features, elemental analysis can be indicative. This presumptive test is made possible by applying scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) in conjunction with an X-ray spectral database recently developed by the FBI laboratory. This database includes spectra for many different materials including known examples of bone and tooth from many different contexts and representing the full range of taphonomic conditions. Results of SEM/EDS analysis of evidence can be compared to these standards to determine if they are consistent with bone and/or tooth and, if not, then what the material might represent. Analysis suggests that although the proportions and amounts of calcium and phosphorus are particularly important in differentiating bone and tooth from other materials, other minor differences in spectral profile can also provide significant discrimination. Analysis enables bone and tooth to be successfully distinguished from other materials in most cases. Exceptions appear to be ivory, mineral apatite, and perhaps some types of corals.     

Mandibular ramus height as an indicator of human infant age

There were two goals to be achieved from the analysis of 53 skeletonized infants from the Southwest Collection at the National Museum of Natural History. The first objective was to determine whether this infant sample could be aged based on a mandibular measurement. The second was to determine which dimension of the mandible, if any, most accurately predicts infant age within a six-month range. Seven osteometric measurements were applied to each mandible. Statistical analysis determined that the individuals in the Smithsonian's Southwest Collection that were under two-years-old could be accurately aged to within six months. Out of these seven measurements the most accurate age-at-death estimates were generated based on the maximum height of the mandibular ramus. This finding can potentially aid investigators in determining the age-at-death of infants.     

Validation of chest X-ray comparisons for unknown decedent identification

Comparing skeletal structures between antemortem and postmortem chest radiographs is widely used by forensic specialists from many disciplines to positively identify unknown decedents. However, validity assessments of this method have been fairly limited. This study had three objectives: 1) to quantify the reliability of ante- and postmortem chest radiograph comparison for decedent identification; 2) to identify useful radiologic features supporting decedent identification; and 3) to recognize sources of error in decedent identification related to use of comparative radiographs. A forensic pathologist, a forensic anthropologist, and two radiologists participated in the study. Our results showed that chest radiograph comparisons proved reliable, if basic decedent information was provided, and antemortem and postmortem radiographs were adequately positioned and exposed. A "morphological approach" using normal anatomical structures for comparison may provide the most efficient method for accurate identification.     

Role of alcohol in heroin overdose

The relationship between ethanol and risk of heroin overdosage was studied. Statistical processing of the results of forensic chemical analysis (460 expert evaluations) carried out in Chelyabinsk Regional Bureau of Forensic Medical Expert Evaluations in 2000 was carried out. The results of morphine and ethanol measurements in the blood and urine from corpses where deaths ensued from narcotic or ethanol poisoning, were analyzed. The concentrations of morphine in the blood and urine were measured on a gaseous chromatographer with mass-selective detector (Hewlett Packard HP 6890/HP-5972). Methods for measuring urinary and blood morphine are described. The results of statistical analysis demonstrated relationships between the age and ethanol concentrations in the blood and urine; blood ethanol and total urinary and blood morphine concentrations; blood concentration of free morphine and presence of 6-monoacetylmorphine in the blood. The authors conclude that the presence of ethanol in the blood together with morphine drastically augments the risk of rapid death from respiration arrest. It can also lead to a relatively high risk of overdosage in experienced narcomaniacs using heroin and ethanol.     

Analysis of ionic ratios in myocardial tissue and their relation to cardiac damage

The authors evaluated the usefulness of the postmortem biochemical analysis of ionic ratios in different parts of the heart and their relation to cardiac damage caused by chest trauma, as observed by anatomopathologic study. Fifty-nine 59 cases were studied, selected from routine necropsies, and samples were taken from different sites of cardiac tissue. The cause of death was trauma in 40 cases and nontraumatic causes in 19 cases. The object of this study was to analyze the levels of Na+, K+, Ca+2, Mg+2, and Zn+2 in different zones of the heart, and the relationship between intracellular and extracellular ion ratios and the different causes of death and any anatomopathologic alterations observed. The biochemical tests revealed a possible relation between the ionic values and cause of death. Alterations in cell membrane permeability and corresponding modification of the ionic ratios were produced earlier than histologic alterations, which need longer to establish themselves whether or not they follow a traumatic process.     

Population genetics of nine short tandem repeat loci: allele frequency distribution in a Brazilian population sample

Gene and genotype frequencies in relation to the D3S1358, vWA, FGA, TH01, TPOX, CSF1PO, D5S818, D13S317, and D7S820 loci were determined in a sample of 290 unrelated individuals (204 Caucasians and 86 mulattoes) living in the city of S?o Paulo, Brazil. The sex test Amelogenin was also performed in all subjects from our sample, revealing the expected sex in all instances. Allele frequency data obtained from the analysis of these samples were in the usual range of other population groups with similar racial background. In the sample of Caucasian individuals, panmictic proportions were ruled out in relation to TPOX and CSF1PO loci, but only in the latter was the overall frequency of heterozygotes significantly less than expected. In the sample of mulattoes, Hardy-Weinberg proportions were rejected in relation to FGA and CSF1PO loci, but in no instance were the overall numbers of heterozygotes different from the corresponding expected ones under panmixia. Taking into account all this and also the number of tests performed, the degree of genetic heterogeneity of Brazilian populations, and the critical level reached by the significant results (1% < alpha<5%), the departures from panmixia here observed can be considered to be negligible in altering significantly biologic relationship odds calculated under the assumption of random matings.     

A new improved method for extraction of DNA from teeth for the analysis of hypervariable loci

A new method for better recovery of DNA suitable for amplification of hypervariable loci from fragments of teeth, consisting of two steps-scraping and aspiration, and extensive decalcification-is reported. Higher yields of high molecular weight DNA were obtained from the root, pulp, and crown of all kinds of 120 teeth, irrespective of gender, age, and source of teeth. HLA DQA1, 5 poly markers (LDLR, GYPA, HBGG, D7S8, and Gc), and other 12 short tandem repeat loci (HPRTB, F13B, LPL, D13S317, D7S820, D5S818, D21S11, D18S51, FGA, D8S1179, D3S1358, and vWA) could be successfully amplified and typed from recovered DNA.     

Rethinking the Probative Value of Evidence: Base Rates,Intuitive Profiling,and the “Postdiction” of Behavior

It is argued that American courts may be routinely admitting evidence with little to no probative value and great potential for prejudicial impact. This may be particularly likely with regard to what is essentially intuitive profiling or stereotype related evidence, defined herein as evidence suggesting that the defendant (or other party), or his (her) behavior, fits intuitive profiles (or stereotypes) of the type of person likely to commit the crime or behavior in question. In other words, intuitive profiling evidence is admitted to postdict behavior. Formal empirically based profiling evidence (testimony regarding the fit of a defendant's characteristics or behaviors to formal or scientific profiles of the typical perpetrator of the crime in question for use to prove guilt is inadmissible in American courts. However, we suggest that everyday use of informal intuitive profiles underlies both judicial determinations of probative value diagnosticity, and thus admissibility, of evidence, and jurors' use of the evidence in determining guilt. Demonstrations of the use of base rate information to evaluate the probative value of such intuitive profiling evidence both as evidence of guilt and as evidence of innocence are provided. Demonstrations of both how to evaluate the actual probative value of evidence (when all necessary values are known), and the theoretical limit of its probative value (in circumstances where some values are not known) are provided. It is argued that such evaluations may provide the basis for (1) support of motions to either admit or to exclude evidence, (2) testimony to the jury to help them weigh or interpret evidence, (3) exculpatory profiling (profiling evidence of innocence), (4) pretrial research to establish probative versus prejudicial value of evidence, and (5) sufficiency analyses to determine maximum likelihood of guilt, given multiple items of evidence. Among these, the first two are considered most important, as it can be demonstrated that many profiling characteristics currently admitted in trial (such as evidence of battery to support a murder charge) are not probative of guilt.