Validation of a 16-locus fluorescent multiplex system

STR multiplexes have been indispensable for the efficient genotyping of forensic samples. The PowerPlex 16 System contains the coreCODIS loci, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, CSF1PO, FGA, THOI, TPOX, vWA, the sex determinant locus, amelogenin, and two pentanucleotide STR loci, Penta D and Penta E. This multiplex satisfies the locus requirements for most national databases and is the most efficient currently available system due to its single PCR amplification. To provide the groundwork for judicial acceptance, including the publication of primer sequences, and to evaluate laboratory-to-laboratory variation, a developmental validation for casework on this commercially available system was performed in 24 laboratories and produced the following conclusions. Amplification was reliable on a variety of thermal cyclers and product could be analyzed on either an ABI PRISM 310 Genetic Analyzer or an ABI PRISM 377 DNA Sequencer. Genotyping using single source samples was consistent between 0.25 and 2 ng of input DNA template with a few laboratories obtaining complete genotypes at 0.0625 ng. However, heterozygote allele imbalance (<60% peak height balance) caused by stochastic effects was observed at a rate of 13% with 0.125 ng DNA and 22% at 0.0625 ng DNA. Mixture analyses were done using a total of 1 ng of DNA template. Most alleles were detected in mixtures of 4 to 1 and some minor alleles were detected in mixtures of 19 to 1. Optimum amplification cycle number was dependent on the sensitivity of the detection instrument used and could also be adjusted to accommodate larger amounts of DNA on solid supports such as FTA paper. Reaction conditions including volume, annealing temperature, and concentrations of primer, AmpliTaq Gold, and magnesium were shown to be optimal yet robust enough to withstand moderate variations without affecting genotype analysis. Environmental, matrix and standard source analyses revealed an ability to obtain complete genotypes in all sample types except those exposed to 80 degrees C for 12-48 days. Finally, comparison of genotype results from the PowerPlex 16 System with other commercially available systems on non-probative reference and forensic samples showed consistent results.     

Driver and front seat passenger fatalities associated with air bag deployment. Part 2: A review of injury patterns and investigative issues

Assessment of the role of air bag deployment in injury causation in a crash of any severity requires analysis of occupant, vehicle, and impact data. The potential injurious role of an air bag is independent of crash severity and is more obvious in minor collisions, particularly those involving "out-of-position" occupants. Factors such as occupant height and other constitutional and medical factors, intoxication, age, type, and proper use of other restraint systems, pre-impact braking and multiple impacts can contribute to an occupant being "out-of-position." Two injury mechanisms are described in out-of-position occupants: "punch-out" when the individual covers the air bag module before deployment and "membrane-force" when the occupant contacts a partly deployed air bag. Each mechanism is associated with injury patterns. In adults, "punch-out" can cause thoraco-abdominal trauma and "membrane-force" loading can lead to craniocervical injury. This can also occur in short-statured occupants including children subjected to both types of loading. In more severe collisions, other factors, e.g., intrusion, steering column and seatbelt loading and other occupant compartment contacts, can contribute to trauma.     

What is the best sample for determining the early postmortem period by on-the-spot flow cytometry analysis?

The level of degradation of DNA as a means for determining the time of death has been proposed as a valid adjunct to the classic thanatochronologic methods. The twofold aim of this work was to determine which organ might reveal both a correlation between the percentage of degradation of the DNA and the time lapse since death, and would be easiest to sample and yield the most reproducible results even in technically unfavorable situations such as on-the-spot investigations at the scene of death. A comparison of the spleen, blood, and liver showed that hepatic tissue best meets these specific needs because it shows a virtually linear correlation between the time elapsed since death and the level of degradation of the DNA, and it can easily be sampled at the scene of death by use of a common biopsy needle.     

Personal identification based on radiographic vertebral features

Personal identification of human remains constitutes about 10% of the normal caseload of any forensic medicine practice. Identification can be achieved by a variety of methods, one of which is the comparison of antemortem and postmortem radiographs. There are numerous accounts of cranial and dental radiographic features useful for identification, whereas the availability of postcranial radiographs and especially plates that depict the vertebral column is less widespread among the forensic community. The authors here review the various vertebral features instrumental in positive identification that can be identified on radiographs of the spine.     

Death resulting from ruptured cerebral artery aneurysm: 219 cases

To characterize the demographics of ruptured cerebral artery aneurysm as a cause of death and to examine the effect of improved diagnostic and therapeutic techniques on the incidence of sudden death associated with the condition, the authors reviewed 219 autopsies performed at the Dallas County Medical Examiner's Office between 1977 and 1997 in which the cause of death was ruptured cerebral artery aneurysm. Ruptured cerebral artery aneurysms accounted for 1.5% of 15,033 natural deaths and 0.4% of all deaths (45,492) followed by autopsy during this period. The majority (56%) of cases occurred in females, with Caucasian females composing the largest group (38%). Seventy-seven percent of cases occurred in individuals between the ages of 31 and 70 years, with the highest concentration in the 41- to 50-year decade (29%). The most common location for ruptured aneurysms was the middle cerebral artery distribution (39%). Multiple aneurysms occurred in 22 (9.1%) cases. Other factors, such as medical history, coexisting disease, symptoms, activity at onset of symptoms, survival time, and toxicology results are also presented. Compared with literature reports before 1980, when ruptured cerebral artery aneurysms were reported as the cause of death in approximately 4% to 5% of sudden natural deaths, the results of this study suggest that despite improved diagnostic and therapeutic techniques during the past two decades, morbidity and mortality from ruptured aneurysms remain a significant health problem.