Editors' Note

Introduction

Editors' Note     

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.     

Surface sterilization of a maggot using bleach does not interfere with mitochondrial DNA analysis of crop contents

Mitochondrial DNA analysis of a maggot crop can identify the corpse a maggot has been feeding on. Analysis of the crop could be useful in a criminal investigation if maggots are found at a suspected crime scene in the absence of a body, or if there is a question of whether a maggot used in postmortem interval estimations moved onto the corpse from another food source. Such analysis can also resolve a chain of custody dispute if it has been suggested that larval samples have been switched. When recovering DNA from a maggot crop, the analyst must be careful to avoid external contamination. We investigated the effects of three simple wash methods developed to reduce external contamination. Maggots raised on pig liver and intentionally contaminated with cow blood were washed using water, 20% bleach, or a solution containing the enzyme DNase. Only washing the maggots in 20% bleach reduced the amount of vertebrate DNA amplified from the maggots' exteriors. No wash method affected the ability to recover DNA from the maggot crops.     

Estimation of body exposure to explosion

An ordnance-disposal expert was killed while disposing of a cache of explosives. The likely position of the body was reconstructed by modeling the explosion as an omnidirectional emission of particles from a model of the explosion site and noting the distribution of particles on a model of a human. The applications and limitations of this method in reconstructing the events and correlation with the injuries noted at autopsy are discussed.     

Fatal salmonella aortitis with mycotic aneurysm rupture

Salmonellae most commonly cause uncomplicated cases of gastroenteritis but have a predilection for damaged blood vessels, especially those damaged by atherosclerosis. The abdominal aorta is most frequently affected. The most serious complication of aortitis is mycotic aneurysm formation with subsequent rupture. The authors present the case of a 61-year-old man who was found unresponsive at home 3 days after discharge from the hospital for treatment of gastroenteritis with bacteremia. Postmortem examination revealed a ruptured mycotic aneurysm with a large retroperitoneal hematoma. Numerous gram-negative rods were embedded in the wall of the aorta and surrounding inflammatory infiltrate, compatible with the patient's previously isolated. Whereas abdominal aortic aneurysm rupture is most commonly associated with atherosclerosis, the isolation of from blood cultures, coupled with radiographic evidence of gas surrounding the aorta, should raise the suspicion of infectious aortitis. Whereas fatal rupture of an aortic aneurysm secondary to atherosclerosis alone or in conjunction with aortitis will not have an impact on the manner of death, infections are reportable and thus have public health implications.     

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.