A Molecular Method to Detect Wound Cells in Bloodstains Resultant of Sharp Force Injuries for Crime Scene Reconstruction.

Previous research by the authors on an animal model showed that bloodstains can contain additional information about their somatic origin in the form of wound cells. Bloodstains produced by a gunshot wound to the head were distinguished from bloodstains produced by a gunshot wound to the chest by testing the stains for a brain microRNA marker. In this study, the effectiveness of the technique was examined on blood drops shed externally from a stab wound to the liver of rat carcasses. Specifically, investigations were conducted on the liver microRNA marker, rno-mir-122-3p, with the QIAGEN miScript System, and PCR analysis. Between the two stabbing methods used, 67% of the scalpel blades and 57% of the blood drops tested positive for rno-mir-122-3p; however, other samples tested negative giving inconclusive results as to the wound-of-origin. The amount of the liver cells in the bloodstains appeared to be related to the extent of trauma.

A molecular method to correlate bloodstains with wound site for crime scene reconstruction.

Bloodstain pattern analysis to determine the wound-of-origin of bloodstains is problematic with nonspecific patterns. In this proof-of-concept study, the authors examined a molecular approach to correlate bloodstains with injuries using the rat as a model. Specifically, investigations were conducted on the rat brain marker, rno-miR-124-3p, with the QIAGEN miScript System and real-time PCR analysis. Rno-miR-124-3p was detected in brain homogenates diluted 100,000 times; in 3-week-old, room temperature stored, simulated brain-blood stains; and in bloodstains from head gunshot wounds collected with swabs and subsequently frozen for 9-18 months; however, rno-miR-124-3p was not detected in whole blood. Proof-of-principle was demonstrated by the ability to distinguish bloodstains from a gunshot wound to the head versus bloodstains from a gunshot wound to the chest, by the testing of otherwise identical bloodstains from the two patterns for the presence of the marker. The results suggest a viable approach to a longstanding problem in casework.

A comparison of the effectiveness of swabbing and flossing as a means of recovering spermatozoa from the oral cavity.

This study examined whether flossing the teeth is a more effective collection method in recovering spermatozoa than conventional swabbing techniques. It was hypothesized that inclusion of flossing as a collection method would extend the recovery of spermatozoa to longer postcoital intervals (PCIs). Eighteen individuals provided 174 oral cavity samples. Successful recovery of spermatozoa was assessed with respect to the collection method and reported activity in the oral cavity during the PCI. Samples were subjected to a differential extraction procedure prior to microscopic evaluation of the extracted pellet. The results indicate that swabbing is more effective than flossing when the PCI falls within 1.5-12 h. However, spermatozoa were recovered from seven floss samples where the corresponding swabs gave negative results. When combining the results from the two collection methods, the percentage of subjects from whom spermatozoa are recovered increases for each PCI beyond the 0-h interval.

Effect of forensic evidence on criminal justice case processing.

This study examined the role and impact of forensic evidence on case-processing outcomes in a sample of 4205 criminal cases drawn from five U.S. jurisdictions. Regression analyses demonstrated that forensic evidence played a consistent and robust role in case-processing decisions. Still, the influence of forensic evidence is time- and examination-dependent: the collection of crime scene evidence was predictive of arrest, and the examination of evidence was predictive of referral for charges, as well as of charges being filed, conviction at trial, and sentence length. The only decision outcome in which forensic evidence did not have a general effect was with regard to guilty plea arrangements. More studies are needed on the filtering of forensic evidence in different crime categories, from the crime scene to its use by investigators, prosecutors, and fact-finders, and to identify factors that shape decisions to collect evidence, submit it to laboratories, and request examinations.

STR melting curve analysis as a genetic screening tool for crime scene samples.

In this proof-of-concept study, high-resolution melt curve (HRMC) analysis was investigated as a postquantification screening tool to discriminate human CSF1PO and THO1 genotypes amplified with mini-STR primers in the presence of SYBR Green or LCGreen Plus dyes. A total of 12 CSF1PO and 11 HUMTHO1 genotypes were analyzed on the LightScanner HR96 and LS-32 systems and were correctly differentiated based upon their respective melt profiles. Short STR amplicon melt curves were affected by repeat number, and single-source and mixed DNA samples were additionally differentiated by the formation of heteroduplexes. Melting curves were shown to be unique and reproducible from DNA quantities ranging from 20 to 0.4 ng and distinguished identical from nonidentical genotypes from DNA derived from different biological fluids and compromised samples. Thus, a method is described which can assess both the quantity and the possible probative value of samples without full genotyping.

Isolation and individualization of conceptus and maternal tissues from abortions and placentas for parentage testing in cases of rape and abandoned newborns.

Abortion specimens are often submitted to forensic laboratories as the only piece of physical evidence in rape and incest cases. The recovery of conceptus tissues from this evidence permits the use of paternity testing to evaluate suspects. In cases of abandoned newborns, the recovery of maternal tissue from the placenta allows for the direct comparison of genetic profiles between the suspected mother and the biological mother. We report on the identification and isolation of conceptus tissues from embryonic- and fetal-period abortions, and maternal tissues from delivered placentas, by gross and low-magnification examination with manual dissection. Hundreds of single-source samples have been successfully recovered by this method and short tandem repeat typed using standard forensic procedures. We additionally describe extraembryonic tissues that can be recovered and typed in the absence of the embryo proper. We conclude that an expertise and protocols can be developed by forensic laboratories for the routine analysis of this evidence.

Variation in nuclear DNA concentrations during urination.

This study examined the cellular origin and concentration of nuclear DNA in human urine. Ten subjects provided two entire, first-morning voids: one as a single specimen and one as a consecutive series of samples. The serial samples were centrifuged, organically extracted, and quantified by slot-blot analysis. Total DNA concentrations ranged from 0.02 to 21.3 ng/mL for the males and 25.0 to 96.9 ng/mL for the females. The female samples were found to contain numerous vaginal epithelial cells. DNA was detected in all of the serial samples of nine subjects; however, the DNA concentrations varied considerably. With six subjects, the DNA concentration of the first serial sample was at least three times greater than that of the entire void. DNA was only detected in the first 21% of the void from one male subject. The results of this study have implications for the collection of urine samples.

STR-typing of human DNA from human fecal matter using the QIAGEN QIAamp stool mini kit.

The purpose of this study was to compare the effectiveness of the QIAGEN QIAamp Stool Mini Kit against a standard phenolchloroform procedure for the extraction, quantitation, and STR-typing of human nuclear DNA from human feces. Stools from six subjects were sampled by swabbing and excision. Samples extracted with the QIAamp kit gave a wide range of DNA yields, whereas those extracted by the organic method yielded no DNA. DNA was not recovered from one subject's stools by either procedure. The QIAamp extracts were amplified with the Profiler Plus and COfiler kits, and PCR inhibition was observed with DNA extracts that were further concentrated. Substitution of water or TE-4 for the QIAamp elution buffer eliminated most, if not all, of the inhibition. A modified QIAamp procedure was used to extract thirty samples, which were subjected to one of five environmental conditions. DNA was recovered from all of these samples, and typing results were obtained on 93% of the samples.