Forensic Articles

Sexual assaults create significant health and legislative problems for every society. All health professionals who have the potential to encounter victims of sexual assaults should have some understanding of the acute and chronic health problems that may ensue from an assault. However, the primary clinical forensic assessment of complainants and suspects of sexual assault should only be conducted by doctors and nurses who have acquired specialist knowledge, skills, and attitudes during theoretical and practical training.

This review presents the basic problems and currently available molecular techniques used for genetic profiling in disaster victim identification (DVI). The environmental conditions of a mass disaster often result in severe fragmentation, decomposition and intermixing of the remains of victims. In such cases, traditional identification based on the anthropological and physical characteristics of the victims is frequently inconclusive. This is the reason why DNA profiling became the gold standard for victim identification in mass-casualty incidents (MCIs) or any forensic cases where human remains are highly fragmented and/or degraded beyond recognition. The review provides general information about the sources of genetic material for DNA profiling, the genetic markers routinely used during genetic profiling (STR markers, mtDNA and single-nucleotide polymorphisms [SNP]) and the basic statistical approaches used in DNA-based disaster victim identification. Automated technological platforms that allow the simultaneous analysis of a multitude of genetic markers used in genetic identification (oligonucleotide microarray techniques and next-generation sequencing) are also presented. Forensic and population databases containing information on human variability, routinely used for statistical analyses, are discussed. The final part of this review is focused on recent developments, which offer particularly promising tools for forensic applications (mRNA analysis, transcriptome variation in individuals/populations and genetic profiling of specific cells separated from mixtures).

Crime Laboratories routinely process evidence from criminal cases for the presence of biological fluids such as blood, semen, and saliva in order to obtain DNA profiles. Forensic Biology encompasses both Forensic Serology and DNA testing. Prior to examination, it is important for the forensic scientist to evaluate the type of crime and the samples submitted so that the evidence can be processed in the proper order for the type of testing needed. Typically, evidence will be analyzed using a mix of presumptive and confirmatory tests to determine the presence of biological stains prior to DNA analysis, although this may not always be feasible when the amount of sample is limited. These Forensic Serology tests assist the analyst in determining which samples will go forward to DNA testing. Forensic DNA testing in most crime laboratories in the United States is done using short tandem repeat (STR) analysis of the 13 core CODIS STR loci. This chapter introduces routine serology procedures, the DNA testing process, the interpretation of DNA profiles, and the national DNA database, CODIS.

Over the last decade, the public has become more aware of the power of DNA typing. Several infamous identity cases have been covered extensively in the media, including the murder trial of O. J. Simpson, the President Clinton –Monica Lewinsky blue dress scandal, the identification of the remains of the tomb of the unknown soldier, the identification of the Romanoff family remains, and the identification of slave-born descendents of the third president of the United States, President Thomas Jefferson. Most recently, DNA identification techniques have been brought to the forefront because of the tremendous task of finding and identifying remains of the victims of the September 11, 2001 terrorist attacks. After the attacks, more than 20,000 total biological samples were recovered combined from the rubble of the World Trade Center, the soil at the site of the United Flight 93 crash in Somerset, PA, and from the American Airlines Flight 77 Pentagon crash site. Biological material recovered from the scenes consisted primarily of bone, teeth, and small samples of soft tissue, which ranged from fresh, to gangrenous, to carbonized. However, reference samples brought from family members included bloodstains, toothbrushes, hair, clothing items, and razors. In the case of this mass disaster, the role of DNA should not be understated —as of December 2002, of the total number of victim identifications made, approx 38% were made exclusively with DNA evidence. Additionally, an approx 40% of the identifications made were through the combined use of DNA along with a more traditional identification method (dental records, personal identifiers, forensic anthropology) (1). Many of these identifications were made from minute amounts of charred, highly degraded biological samples that might have otherwise not been properly identified and returned to the families.

Wildlife DNA forensics is receiving increasing coverage in the popular press and has begun to appear in the scientific literature in relation to several different fields. Recognized as an applied subject, it rests on top of very diverse scientific pillars ranging from biochemistry through to evolutionary genetics, all embedded within the context of modern forensic science. This breadth of scope, combined with typically limited resources, has often left wildlife DNA forensics hanging precariously between human DNA forensics and academics keen to seek novel applications for biological research. How best to bridge this gap is a matter for regular debate among the relatively few full-time practitioners in the field. The decisions involved in establishing forensic genetic services to investigate wildlife crime can be complex, particularly where crimes involve a wide range of species and evidential questions. This paper examines some of the issues relevant to setting up a wildlife DNA forensics laboratory based on experiences of working in this area over the past 7 years. It includes a discussion of various models for operating individual laboratories as well as options for organizing forensic testing at higher national and international levels.

Species identification has become a tool in the investigation of acts of alleged wildlife crimes. This review details the steps required in DNA testing in wildlife crime investigations and highlights recent developments where not only can individual species be identified within a mixture of species but multiple species can be identified simultaneously. ‘?’ is a question asked frequently in wildlife crime investigations. Depending on the material being examined, DNA analysis may offer the best opportunity to answer this question. Species testing requires the comparison of the DNA type from the unknown sample to DNA types on a database. The areas of DNA tested are on the mitochondria and include predominantly the cytochrome gene and the cytochrome oxidase I gene. Standard analysis requires the sequencing of part of one of these genes and comparing the sequence to that held on a repository of DNA sequences such as the GenBank database. Much of the DNA sequence of either of these two genes is conserved with only parts being variable. A recent development is to target areas of those sequences that are specific to a species; this can increase the sensitivity of the test with no loss of specificity. The benefit of targeting species specific sequences is that within a mixture of two of more species, the individual species within the mixture can be identified. This identification would not be possible using standard sequencing. These new developments can lead to a greater number of samples being tested in alleged wildlife crimes.

The science of forensic entomology has had a staggered and interesting history (Nuorteva 1977; Smith 1986; Erzinçlioglu 1990; Marchenko 2001; Amendt et al. 2004). Its main application is the estimation of the postmortem interval (PMI), and Villet et al (this book, Chapter 7) highlight variables that affect insect development and in its consequence the calculation of this postmortem interval. Great strides have been made in basic and applied research, but there are many questions yet to be answered and there is still room for growth, as several other chapters in this book showed. While there is unquestionable the need for much more research to gather well-based data, there is also a need for quality assurance, standards and certification (Melbye and Jimenez 1997). In this chapter, we will discuss a selection of possible future trends in forensic entomology.

Illegal trade of wildlife is growing internationally and is worth more than USD$20 billion per year. DNA technologies are well suited to detect and provide evidence for cases of illicit wildlife trade yet many of the methods have not been verified for forensic applications and the diverse range of methods employed can be confusing for forensic practitioners. In this review, we describe the various genetic techniques used to provide evidence for wildlife cases and thereby exhibit the diversity of forensic questions that can be addressed using currently available genetic technologies. We emphasise that the genetic technologies to provide evidence for wildlife cases are already available, but that the research underpinning their use in forensics is lacking. Finally we advocate and encourage greater collaboration of forensic scientists with conservation geneticists to develop research programs for phylogenetic, phylogeography and population genetics studies to jointly benefit conservation and management of traded species and to provide a scientific basis for the development of forensic methods for the regulation and policing of wildlife trade.

Recombinant DNA technology can provide novel and powerful methods for forensic science application. Human genomic DNA can be analyzed directly for individual identification and paternity testing on the basis of polymorphism in its sequence. Restriction fragment length polymorphism (RFLP) testing, STR (microsatellite) and mitochondrial DNA analysis (mtDNA) is suitable for examination of the forensic biological samples (bloodstains, hairs, seminal stains, bones, tooth). Using a combination of single locus probe (SLP) that varies highly among individuals, a DNA fingerprint or profile can be made. Mitochondrial DNA RFLPs may also suggest the characteristics of the human races.

One of the central questions in a legal trial is whether the suspect did or did not commit the crime. It will be apparent that absolute certainty cannot be attained. Because there is always a certain degree of uncertainty when interpreting the evidence, none of the evidence rules out all hypotheses except one. The central question should therefore be formulated in terms of probability. For instance, how probable is it that the suspect is the offender, given the situation and a number of inherent uncertain pieces of evidence? The answer to this question requires the estimation, and subsequent combination, of all relevant probabilities, and cannot be provided by the forensic expert. What the forensic expert can provide is just a piece of the puzzle: an estimate of the evidential value of her investigation. This evidential value is based on estimates of the probabilities of the evidence given at least two prespecified hypotheses. These probabilities can subsequently be used by the legal decision maker in order to determine an answer to the question above, but they are, of course, not sufficient. They need to be combined with all the other information in the case. A probabilistic framework to do this is the Likelihood Ratio approach for the interpretation of forensic evidence. In this chapter we will describe this framework.

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