Ana Castelló

Bleach interference in forensic luminol tests on porous surfaces: More about the drying time effect

As criminals try to avoid leaving clues at the scene of a crime, bloodstains are often washed away, but fortunately for investigators, they are difficult to eliminate completely. Porous surfaces easily retain blood traces, which are sometimes invisible to the naked eye. The reagent of choice for detecting latent blood traces on all types of surfaces is luminol, but its main disadvantage is a high degree of sensitivity to oxidising contaminants in the blood sample. If household bleach is used to clean bloodstains, presumptive tests are invalidated. Hypochlorites, however, are known to be unstable and deteriorate over time, and this feature could be of help in preventing household bleach-induced interference. Previous studies have evaluated the effect of the drying time on nonporous surfaces, but nothing has as yet been published about this effect on porous surfaces. Consequently, this paper reports on hypochlorite interference with luminol reagents used on this type of surface, evaluating the effects of drying time on the household bleach-luminol reaction, and ascertaining whether the drying procedure could be applied to prevent household bleach interference on bloodstained porous surfaces. The results indicate that the drying method may very well overcome household bleach interference in luminol reaction tests, if the investigation allows for an appropriate waiting time.

Active oxygen doctors the evidence

Investigation at the scene of a crime begins with the search for clues. In the case of bloodstains, the most frequently used reagents are luminol and reduced phenolphthalein (or phenolphthalin that is also known as the Kastle–Meyer colour test). The limitations of these reagents have been studied and are well known. Household cleaning products have evolved with the times, and new products with active oxygen are currently widely used, as they are considered to be highly efficient at removing all kinds of stains on a wide range of surfaces. In this study, we investigated the possible effects of these new cleaning products on latent bloodstains that may be left at a scene of a crime. To do so, various fabrics were stained with blood and then washed using cleaning agents containing active oxygen. The results of reduced phenolphthalein, luminol and human haemoglobin tests on the washed fabrics were negative. The conclusion is that these new products alter blood to such an extent that it can no longer be detected by currently accepted methods employed in criminal investigations. This inability to locate bloodstains means that highly important evidence (e.g. a DNA profile) may be lost. Consequently, it is important that investigators are aware of this problem so as to compensate for it.

Accuracy, Reliability, and Safety of Luminol in Bloodstain Investigation

ABSTRACT The reliability of luminol as a presumptive test reagent was studied in this work. The possibility of obtaining a false negative subsequent to contamination of the test specimen was determined. The behavior of luminol with respect to a contaminant was compared to other reagents used in similar tests. Following an analysis of the test results, other test sensitivity, and safety data, it was concluded that luminol is a more reliable reagent than others due to a higher improbability of producing false positives and false negatives, apart from being safer than other substances. It should, therefore, be considered as a “preferable” or “first choice” reagent for use in presumptive tests.

Solving underwater crimes: Development of latent prints made on submerged objects

Underwater crime scenes always present a challenge for forensic researchers, as the destructive effect of water considerably complicates the chances of recovering material of evidential value. The aim of this study is to tackle the problem of developing marks that have been left on submerged objects. Fingermark deposition was randomly made on two surfaces - glass and plastic whilst the material was submerged under tap water and then left for one to fifteen days before drying and development. For their later development, various reagents - Black Powder, Silver Metallic Powder, Fluorescent Powder, Sudan Black (powder and solution) and Small Particle Reagent - were used and the effectiveness of each of them on this particular type of evidence was then evaluated. The results show the possibility of obtaining good quality developed marks, even under such adverse circumstances. Further and wider research should, therefore, be undertaken in which other variables are introduced such as different substrates, other types of liquids, and environmental or time factors.

The 1258 G>A polymorphism in the neuropeptide Y gene is associated with greater alcohol consumption in a Mediterranean population

Neuropeptide Y (NPY) is a neurotransmitter widely distributed in the central nervous system. Several studies have demonstrated that increases of NPY are associated with reduced alcohol intake and anxiety manifestations. The Leu7Pro polymorphism in the NPY has been associated with alcohol consumption, but evidence is scarce. In the Spanish Mediterranean population, this variant is not polymorphic. Thus, our aim is to identify novel functional variants in the NPY and to investigate the impact of these markers and others previously described on alcohol consumption in this population. A total of 911 subjects (321 men and 590 women) from the Spanish Mediterranean population were recruited. Alcohol consumption, and demographic and lifestyle variables were measured. Nucleotide sequence determination and SNP analyses were carried out. Only one exonic SNP was detected by direct sequencing (1258 G>A or rs9785023; allele frequency 0.47). From the intronic markers chosen (483 A>G or rs13235938, 2517 A>G or rs4722342, and 7065 A>G or rs4722343), only the two latter ones were polymorphic (allele frequencies 0.46 and 0.04, respectively), and none of them were associated with alcohol consumption. However, the 1258 G>A SNP was associated (recessive pattern) with higher alcohol intake. This association was particularly relevant in men with high alcohol intake (59.1±5.0 g/day in AA as opposed to 40.6±7.5 in the G carriers, P=.022) and women with moderate alcohol intake (7.3±5.5 g/day in AA as opposed to 4.6±3.9g/day in G carriers, P=.048). The 1258 G>A polymorphism in the NPY is associated with higher alcohol consumption in the Mediterranean population.

DNA Evidence Uncompromised by Active Oxygen

Currently, forensic sciences can make use of the potential of instrumental analysis techniques to obtain information from the smallest, even invisible, samples. However, as laboratory techniques improve, so too should the procedures applied in the search for and initial testing of clues in order to be equally effective. This requires continuous revision so that those procedures may resolve the problems that samples present. As far as bloodstains are concerned, there are methods available that are recognized as being both highly sensitive and effective. Nevertheless, the marketing of new cleaning products, those that contain active oxygen, has raised doubts about the ability of those procedures to detect blood. It has been shown that stains washed with these detergents (and still visible) invalidated both the presumptive test (reduced phenolphthalein, luminol, and Bluestar®) and that applied for determining human hemoglobin. These findings have caused considerable concern both within the forensic and scientific community, and among the general public, so obliging us to seek solutions. In this work, the effect of these new cleaning products on DNA analyses is studied. The results, encouraging ones, show that these detergents, despite invalidating all other tests, do not hinder the extraction, or the subsequent analysis, of DNA.

Chemistry in crime investigation: sodium percarbonate effects on bloodstains detection.

Abstract:  Chemistry plays a leading role in crime investigation. In the study of bloodstains, chemical reactions provide the means for the detection. All these procedures have been thoroughly studied. However, recently, a new source of error has been found: washing stains with “active oxygen” detergents abrogates presumptive and human hemoglobin tests for bloodstains (although visible). The aim of this investigation was to evaluate the ability of pure sodium percarbonate—main component of detergents—to abrogate presumptive and human hemoglobin tests. Then, a solution to this problem could be found. The results demonstrate that pure sodium percarbonate—itself—is able to abrogate all tests, as well as the different degrees to which each of them is affected by the product. Consequently, faced with a stain of bloody appearance, even the preliminary tests are negative; it is advisable to analyze the DNA. Otherwise, the opportunity of obtaining valuable information is lost.

Association between Opioid Receptor mu 1 (OPRM1) Gene Polymorphisms and Tobacco and Alcohol Consumption in a Spanish Population.

Evidence gained from animals and humans suggests that the encephalic opioid system might be involved in the development of drug addiction through its role in reward. Our aim is to assess the influence of genetic variations in the opioid receptor mu 1 on alcohol and tobacco consumption in a Spanish population. 763 unrelated individuals (465 women, 298 men) aged 18-85 years were recruited between October 2011 and April 2012. Participants were requested to answer a 35-item questionnaire on tobacco and alcohol consumption, as well as to complete the AUDIT and Fagerström tests. Individuals were genotyped for three polymorphisms in the opioid receptor mu 1 (OPRM1) gene, using a TaqMan protocol. In males, the rs10485057 polymorphism was associated with total pure ethanol intake and with the risk of being an alcohol consumer. Also, this polymorphism was significantly associated with higher Fagerström scores. Rs1799971 had a different influence on adaptive and maladaptive patterns of alcohol use. Despite the limited sample size, our study might enrich current knowledge on patterns of alcohol use, because it encompasses both extreme and adaptive phenotypes, providing thus a wider perspective on this subject.

PPAR-α L162V and PGC-1 G482S gene polymorphisms, but not PPAR-γ P12A, are associated with alcohol consumption in a Spanish Mediterranean population

BACKGROUND Peroxisome Proliferator-Activated Receptors (PPARs) and its co-activators are regulatory elements of the cellular lipid homeostasis and have been associated with feeding behavior modulation. Animal models suggest that these genes may be involved in alcohol consumption regulation. However, no studies in humans exist. Our aim is to estimate the possible association between polymorphisms in the PPAR-alpha, PPAR-gamma and PPAR-gamma co-activator 1A (PGC-1A) genes and alcohol consumption in humans. METHODS We have conducted a cross-sectional study between the PPAR-alpha L162V, PPAR-gamma P12A and PGC-1A G482S polymorphisms, and alcohol consumption in a general Mediterranean Spanish population (303 men and 443 women). RESULTS We have found an association between the L162V polymorphism and alcohol consumption in which, carriers of the V allele were more prevalent among alcohol consumers (19.4% vs. 9.8%; OR 2.69; 95% CI: 1.31-5.54, p=0.007). The G482S polymorphism showed a significantly higher frequency in the group of high alcohol drinkers than in non-high alcohol drinkers (33.4% vs. 20.6%; OR 2.28; 95% CI: 1.07-4.88, p=0.034). Mean alcohol consumption was higher as the number of G alleles increased (GG 8.6+/-12.8 g/day, GS 6.6+/-9.2 g/day, SS 5.6+/-7.8 g/day, p=0.003). These results remained statistically significant after covariate adjustment. CONCLUSIONS PPAR-alpha L162V and PGC-1A G482S polymorphisms are associated with alcohol consumption in the Mediterranean population.

More about RSID-saliva: the effect of sample age and the environment on the test’s efficacy

In addition to the genetic profile of the donor, body fluid stains can provide forensic scientists with a lot of other information. Knowing the nature of these fluids can be fundamental in categorising a crime and reconstructing the events involved. To do so, it is necessary to have the means to confirm the origin of the body fluids. Prepared commercial kits to evaluate haemoglobin and prostate-specific antigen have been utilised for many years in forensic laboratories. The RSID-saliva test performs a similar function in the determination of this body fluid. The test’s sensitivity and specificity have been confirmed in previous studies, but in order to apply it to real samples it is also necessary to evaluate its efficacy on fluids exposed to real conditions of deterioration. The present study deals with mock casework samples, introducing the factors of the age of the sample and the effect of contact with the environment. The influence of the type of material is also evaluated. The results show the resistance to these factors of 40-day-old saliva samples. Consequently, in the study conditions, positives can be obtained using RSID-saliva. Thus, the data provided indicate that RSID-saliva is a useful forensic test for examining evidentiary items suspected of containing saliva.