Forensic Science Casework Research Articles

Evaluating forensic DNA evidence: Connecting the dots

AbstractTechnological developments within the field of forensic genetics have enhanced the sensitivity and specificity of DNA testing tremendously and have broadened the applications of biological evidence in criminal investigations. Evaluation and communication of the evidential findings within criminal cases have not maintained the same pace, which has largely stemmed from a failure to adopt a standardized approach within and across the various fields of forensic science. Within forensic biology, this has led to unjustified opinions on the weight of the evidence and occurrences of the association fallacy, when the weight of evidence given propositions at one level of the hierarchy of propositions is inappropriately transposed to a higher level. We further define the association fallacy to include the terms, “source level fallacy” and “activity level fallacy,” to enable the forensic science community to better identify and address issues in biological evidence evaluation. It is important to understand these concepts and their causes, and in doing so, identify potential avenues to avoid these fallacies in forensic science casework. These avenues include training and education of forensic and legal professionals, as well as research into transfer, persistence, prevalence and recovery (TPPR) of DNA and biological evidence in general.This article is categorized under: Forensic Biology > Interpretation of Biological Evidence

Forensic Investigation and Comparison of Blood Sample Referring to Thalassemia

Identification of an individual is one of the significant features of forensic investigation. The present study was conducted to study the difference between normal and thalassemic blood. The study was conducted on 40 blood samples aim to compare control and disease wet blood samples by using different methods of microscopy. The comparison was done based on the morphology of the RBCs and red blood cell count. A (monolayer) thin blood film is prepared on a slide with a wet blood sample and observed under a compound microscope. Red blood cell count is performed with the help of Neubauer’s chamber. Observation shows the changes in the morphology of red blood cells in the thalassemic population as compared to the control population, moreover based on total RBCs count the number red blood cell count found higher in the thalassemic population as compared to the control. Both morphology and Count significantly differed from the control population. Thus, the present method can be used in the daily routine at forensic science casework.

The study of ABO genotyping for forensic application

ABO blood typing has been used for personal identification and paternity testing in forensic medicine and criminal investigations for many years, since the ABO blood types obtained from evidentiary samples are usually one of the initial pieces of information available that could lead to identification of the suspect. Because of this importance of the initial information, many different molecular typing methods have been reported to complement routine serological ABO blood typing in forensics. The method using a multiplex allele-specific primer set enables the detection of six SNP sites in the ABO gene (nt 261, 526 and 803) along with the determination of ABO genotypes from their combinations, which is applied to forensic science casework samples in this paper. An internal validation study has been conducted to show that this method successfully determined ABO genotypes of blood, blood stain, saliva stain, buccal swab, vaginal fluid, hair and low copy number sample with high sensitivity, accuracy, and reproducibility. These results suggest that the method using a multiplex allele-specific primer set is so reliable that it can be used as a rapid screen for forensic science casework samples before multi locus short tandem repeat (STR) profiling is performed.

DNA profiles from clothing fibers using direct PCR.

We report on the successful use of direct PCR amplification of single fibers from items of worn clothing. Items of clothing were worn throughout the course of a day, with the individual commencing regular activities. Single fibers were taken from the cuff of the clothing at regular intervals and amplified directly. The same areas were subjected to tape-lifting, and also amplified directly for comparison. The NGM™ kit that amplifies 15 STR loci plus amelogenin was used. A total of 35 single fiber samples were processed and analyzed from five items of clothing, with 81% of samples returning a profile of 14 alleles or more. All tape-lift samples amplified directly produced DNA profiles of 15 alleles or more. The aim was to develop a simple, operational method that could be used routinely in forensic science casework and that has the potential to generate more complete profiles, which would not be detected using standard extraction methods on this type of sample. For ease of implementation, the process also adheres to standard methods with no increase in the cycle number.

The end of the (forensic science) world as we know it? The example of trace evidence.

The dominant conception of forensic science as a patchwork of disciplines primarily assisting the criminal justice system (i.e. forensics) is in crisis or at least shows a series of anomalies and serious limitations. In recent years, symptoms of the crisis have been discussed in a number of reports by various commentators, without a doubt epitomized by the 2009 report by the US National Academies of Sciences (NAS 2009 Strengthening forensic science in the United States: a path forward). Although needed, but viewed as the solution to these drawbacks, the almost generalized adoption of stricter business models in forensic science casework compounded with ever-increasing normative and compliance processes not only place additional pressures on a discipline that already appears in difficulty, but also induce more fragmentation of the different forensic science tasks, a tenet many times denounced by the same NAS report and other similar reviews. One may ask whether these issues are not simply the result of an unfit paradigm. If this is the case, the current problems faced by forensic science may indicate future significant changes for the discipline. To facilitate broader discussion this presentation focuses on trace evidence, an area that is seminal to forensic science both for epistemological and historical reasons. There is, however, little doubt that this area is currently under siege worldwide. Current and future challenges faced by trace evidence are discussed along with some possible answers. The current situation ultimately presents some significant opportunities to re-invent not only trace evidence but also forensic science. Ultimately, a distinctive, more robust and more reliable science may emerge through rethinking the forensics paradigm built on specialisms, revisiting fundamental forensic science principles and adapting them to the twenty-first century.

Fingermark detection on non-porous and semi-porous surfaces using YVO4:Er,Yb luminescent upconverting particles

This article describes the use of an anti-Stokes luminescent material (upconverter), yttrium vanadate doped with ytterbium and erbium (YVO(4):Er,Yb), for the development of latent fingermarks on a range of non-porous surfaces. Anti-Stokes luminescent materials emit light at shorter wavelengths than the excitation wavelength. This property is unusual in both natural and artificial materials commonly found as exhibits in forensic science casework. As a result, fingermark detection techniques based on anti-Stokes luminescence are potentially extremely sensitive and selective. Latent fingermarks on non-luminescent and inherently luminescent substrates, including Australian polymer banknotes (a well-known 'difficult' surface), were developed with YVO(4):Er,Yb by dry powder and wet powder techniques. The effectiveness of YVO(4):Er,Yb for fingermark detection was compared with that of cyanoacrylate fuming and of sodium yttrium tetrafluoride doped with ytterbium and erbium (NaYF(4):Er,Yb). The results illustrate some benefit of luminescent up-converting phosphors over traditional luminescence techniques for the detection of latent fingermarks.

GC Quantitative Determination of Illicit LSD

Abstract Several methods are used for the determination of LSD in forensic science casework samples. One of these involving a shift in UV absorption maximum is considered too nonspecific to provide unequivocal confirmation of the presence of LSD. Currently, HPLC methods using fluorescence detectors are recommended for quantification and capillary GC/MS is considered a good technique for the qualitative identification of the drug. In this work we demonstrate the possibility of using capillary GC for the quantitative determination of LSD since this method is equally sensitive but surely more flexible and rapid than the HPLC ones.

Restriction Fragment Length Polymorphism Analysis of Forensic Science Casework in the People's Republic of China

Restriction fragment length polymorphism (RFLP) analysis for the purpose of individualization is now being used in casework in the People's Republic of China. This report describes the use of the multilocus minisatellite probe 33.15 to solve three cases, including two homicides and a rape. In the third case, fetal tissue was analyzed to prove that the alleged rapist was, in fact, the father. In each case, analysis of deoxyribonucleic acid (DNA) resulted in a positive match. The probability of chance association of the DNA fingerprint was calculated as 5.6 x 10(-12), which is similar to the figures reported in the literature.

Forensic Applications of the Determination of Benzodiazepines in Blood Samples by Microcolumn Cleanup and High-Performance Liquid Chromatography with Reductive Mode Electrochemical Detection

Recently described microcolumn cleanup and high-performance liquid chromatography with electrochemical reductive mode detection have facilitated the determination of benzodiazepines in contaminated and degraded blood samples. Examples from an extensive application of the procedure to British forensic science casework are given here.

The separation of lysergide (LSD) from related ergot alkaloids and its identification in forensic science casework samples

The separation of lysergide (LSD) from related ergot alkaloids and its identification in forensic science casework samples

A Novel Technique for the Collection and Recovery of Foreign Fibers in Forensic Science Casework

Abstract In criminal investigations, especially in rape, sodomy, and murder cases, forensic scientists are frequently asked to establish a possible transfer of fiber evidence. In such cases, the initial task is to recover the minute fragments of transferred fibers from the surfaces of the textile articles involved in an incident. An ideal method should be simple, rapid, efficient, and reliable. A novel technique satisfying all of the above criteria is described which involves the use of an adhesive bed for the collection and recovery of fibers, and laser illumination/stereo light microscopy for search and localization of possible matching fibers. The adhesive bed consists of a clear polyester film (100 by 130 mm) preprinted with a grid and label. The grid area (100 by 100 mm) was covered with Double Coated® adhesive tape. The bed is stored in a document protector. The advantages of this new technique over existing methods include rapid collection of evidence material from large surfaces, convenient handling and storage of samples, and rapid recovery of suspect fibers. This technique is time-saving and practical in routine cases and meets the needs of overburdened crime laboratories.

Progressive Desialidation of Human Transferrin

Transferrin is a serum glycoprotein which contains four sialic acid residues located at the end of two branched carbohydrate structures. The presence of these four acidic residues influences the electrophoretic mobility of the transferrin molecule. Alterations in the electrophoretic mobility of transferrin may be encountered in forensic science case work, particularly in association with postmortem samples. These altered transferrins usually appear in a highly stylized "ladder" banding pattern. To determine whether these altered transferrins are the result of sialic acid removal, serum samples of known transferrin type were treated with neuraminidase. These experiments support the hypothesis that the "ladder" banding pattern of transferrin observed in some case samples is due to the removal of sialic acid residues by bacterial or endogenous neuraminidase. These studies also demonstrate that partially desialidated transferrin variants cannot be clearly typed until the sialic acid is completely stripped from the transferrin molecule. Reliable typing of partially desialidated samples can be accomplished by treating these samples with neuraminidase.

The Separation of Lysergide (LSD) from Related Ergot Alkaloids and Its Identification in Forensic Science Casework Samples

Abstract The separation of lysergide (LSD) from related ergot alkaloids, and its isomer lysergic acid methylpropylamide (LAMPA), has been investigated using the techniques of capillary gas chromatography and high performance liquid chromatography (HPLC). Capillary gas chromatography using fused silica nonpolar bonded phase columns gave good discrimination, and retention indices for several ergot alkaloids have been measured. The applicability of this technique to the analysis of illicit LSD preparations has been demonstrated by preparing extracts from LSD microdot tablets and card and paper squares. The HPLC systems examined in the present study were unable to achieve baseline resolution of LSD and LAMPA.

A Bayesian Approach to the Problem of Interpreting Glass Evidence in Forensic Science Casework

A new approach is described to the problem of interpreting the evidential value of glass fragments found on the clothing of a person who is suspected of having committed a crime. The problem is described in a formal sense and a brief review is given of previous papers which have been written on the problem. It is then shown how the Bayesian argument can be applied. Numerical examples are given, based on data abstracted from various sources.

The interpretation of refractive index measurements VI: The computer program rung

An approach to the interpretation of glass refractive index measurements in forensic science casework, which has been developed in five previous papers, is concluded with a discussion of the computer program RUNG. This program assists the forensic scientist in assessing the evidential value of refractive index measurements. A detailed practical example of the program is provided.

An Evaluation of Gamma-Glutamyl Transpeptidase (GGT) and p30 Determinations for the Identification of Semen on Postcoital Vaginal Swabs

The following study entails the investigation of gamma-glutamyl transpeptidase (GGT) and p30 for the identification of seminal stains in sexual assault cases. A commercial kit was used to test for GGT activity, while p30 was demonstrated with a crossed electrophoresis technique. Specificity, sensitivity, and stability of both markers were studied. Postcoital swabs from lab staff were tested for GGT and p30. In addition, 144 postcoital swabs from case material were tested for p30, spermatozoa, and acid phosphatase. Results show p30 to be a useful semen marker particularly in cases of azoospermia. However, GGT was found to be unsuitable for forensic science casework.

The interpretation of refractive index measurements V.

An approach to the interpretation of glass refractive index measurements in forensic science casework which has been developed in four previous papers is extended to deal with the calculation of coincidence probabilities in cases which involve multiple control and recovered samples. Examples of the calculations are given and there is a discussion of the possible limitations of the method.

The interpretation of refractive index measurements. IV

An approach to the interpretation of glass refractive index measurements in forensic science casework which has been described in three previous papers is developed further. Three methods of calculating a coincidence probability to assist in the assessment of evidential significance are described and compared. An interactive computer program RUNG has been written which incorporates the results of previous work and also a program for estimating coincidence probabilities. Examples of its operation are given.

The quantitative analysis of glass by inductively coupled plasma-atomic-emission spectrometry: A five-element survey

Approximately 350 glass samples of known origin, encompassing most of the types of glass likely to be encountered in forensic science casework, have been analysed by inductively coupled plasma-atomic-emission spectrometry. The samples included 123 window glasses, 56 vehicle glasses, 91 container glasses and 58 tableware glasses. The analytical procedure provided the quantitative levels of manganese, iron, magnesium, aluminium and barium in the samples. The data for the elemental concentrations, together with refractive index, are presented in histogram form.

A New Approach to the Microscopical Examination and Comparison of Synthetic Fibers Encountered in Forensic Science Cases

Abstract This paper describes a refined approach to the problems of identification and comparison of synthetic fibers encountered in forensic science case work. The necessary apparatus consists of a polarizing microscope equipped with a Mettler hot stage. Observations concerning the variation of a fiber's birefringence with temperature have been found to be very useful, both for determining the generic type of an unknown fiber and for detecting subtle differences among fibers of the same generic type from different sources. Data, including semilogarithmic plots of birefringence as a function of temperature, are given for nine different generic types of synthetic fibers.