The impact of the principles of evidence interpretation on the structure and content of statements

The Forensic Science Service (FSS) has devoted appreciable effort to developing the application of the principles of evidence interpretation. Much of the work has been reported in previous papers in this journal, in particular those that develop a model for Case Assessment and Interpretation (CAI). The principles of interpretation are restated and the implications for structure and content of statements are described.     

DNA profiling of trace evidence--mitigating evidence in a dog biting case

A young girl was the victim of a severe dog attack. An animal, suspected of having caused the attack, was later impounded for investigation. Microclots of blood, recovered from the dog's fur, were analyzed by STR DNA. Results showed that this blood was not related to the biting. Other forensic evidence--hairs, fibers, and odontology--failed to connect a particular animal to the attack. The implications of these findings for the dog and its owners are discussed as well as other forensic methods for resolving such cases.     

浅论科技证据及其在我国刑事诉讼中的运用问题

一、科技证据的涵义及内容 现代科技知识在诉讼程序中虽然早已开始运用,但正式出现"科技证据"(有的学者称"科学证据")一词却是近年来的事,目前国内外对"科技证据"的定义尚无统一的认识.     

A general approach to Bayesian networks for the interpretation of evidence

Bayesian networks (BNs) are mathematically and statistically rigorous techniques for handling uncertainty. The field of forensic science has recently attributed increased attention to the many advantages of this graphical method for assisting the evaluation of scientific evidence. However, the majority of contributions that relate to this topic restrict themselves to the presentation of already "constructed" BNs, and often, only a few explanations are given as to how one obtains a specific BN structure for a given problem. Based on several examples, the present paper will therefore attempt to explain in more detail some guiding considerations that might be helpful for the elicitation of appropriate structures for BNs.     

Investigation into "normal" background DNA on adult necks: implications for DNA profiling of manual strangulation victims

Others have investigated the role that DNA profiling could play as a method for identifying the perpetrator of manual strangulation. These studies have demonstrated that it is possible to collect offender DNA from the skin surface of a victim following physical contact. It is not known whether nonself biological material is normally present on the skin surface due to adventitious transfer occurring during innocent everyday interactions. To test the hypothesis that detectable amounts of nonself DNA are normally present on the skin surface of healthy adult individuals due to the adventitious transfer of DNA occurring during normal day-to-day social interactions, we designed an experiment in three phases. Phase 1 was used to deduce which DNA collection, extraction, and amplification methods were suited to investigating this question. During phase 2, the neck surface of 24 healthy adult volunteers was swabbed. DNA was extracted using the QIAamp DNA mini kit and amplified using the SGM Plus PCR amplification kit, using 28 PCR cycles. The work carried out during phase 3 involved a simulated assault to investigate primary and secondary transfer of DNA during physical contact. It was found that 23% of neck areas swabbed during phase 2 of this investigation showed nondonor alleles in the resulting DNA profile, with 5% of areas showing six or more nondonor alleles. The results of phase 3 showed that primary, secondary, and zero transfer of victim and/or offender DNA could be observed after physical contact and that alleles from an unknown source could still be detected in this more controlled experiment. The data presented in this paper demonstrate that DNA profiles generated after swabbing the skin surface of healthy adults can include components of an unknown source, present due to adventitious transfer. These components, if present in large quantities, have the potential to interfere with DNA profile interpretation of swabs taken for the investigation of physical assault by DNA profiling.     

Recovery of trace DNA and its application to DNA profiling of shoe insoles

In recent years, the analysis of trace amounts of DNA has become a necessary and useful forensic tool. DNA profiles can be obtained from items that have been worn or handled, due to the presence of transferred DNA derived from skin cells. Shoeprints collected from crime scenes that match a suspects shoe can link a shoe to the crime scene. A DNA profile from inside the shoe can link a wearer to a shoe thus increasing the evidential value of the forensic evidence. In this work, variation in the amount of DNA recovered from hands and feet of different individuals is investigated. Sites for sampling DNA from shoe insoles are compared and a protocol for the subsequent sampling and extraction is developed. Finally, a case study is described where DNA analysis of shoe insoles has provided forensic evidence.     

Inferring the population of origin of DNA evidence within the UK by allele-specific hybridization of Y-SNPs

Marked differences in Y-SNP allele frequencies between continental populations can be used to predict the biogeographic origin of a man's ancestral paternal lineage. Using 627 samples collected from individuals within the UK with pale-skinned Caucasian, dark-skinned Caucasian, African/Caribbean, South Asian, East Asian or Middle Eastern appearance we demonstrate that an individual's Y-SNP haplogroup is also strongly correlated with their physical appearance. Furthermore, experimental evaluation of the Marligen Signet Y-SNP kit in conjunction with the Luminex 100 detection instrument indicates that reliable and reproducible haplogrouping results can be obtained from 1 ng or more of target template derived from a variety of forensic evidence types including, blood, saliva and post-coital vaginal swabs. The test proved highly male-specific with reliable results being generated in the presence of a 1000-fold excess of female DNA, and no anomalous results were observed during degradation studies despite a gradual loss of typable loci. Hence, Y-SNP haplogrouping has considerable potential forensic utility in predicting likely ethnic appearance.     

DNA profiling of trace DNA recovered from bedding

Trace DNA is often detected on handled items and worn clothing examined in forensic laboratories. In this study, the potential transfer of trace DNA to bedding by normal contact, when an individual sleeps in a bed, is examined. Volunteers slept one night on a new, lower bed sheet in their own bed and one night in a bed foreign to them. Samples from the sheets were collected and analysed by DNA profiling. The results indicate that the DNA profile of an individual can be obtained from bedding after one night of sleeping in a bed. The DNA profile of the owner of the bed could also be detected in the foreign bed experiments. Since mixed DNA profiles can be obtained from trace DNA on bedding, caution should be exercised when drawing conclusions from DNA profiling results obtained from such samples. This transfer may have important repercussions in sexual assault investigations.     

Y-chromosome STR haplotype profiling in the Korean population

Allele and haplotype frequencies of seven Y-chromosome STR loci were determined from a sample of 330 unrelated males in the Korean population.     

Threat mail and forensic science: DNA profiling from items of evidence after treatment with DFO

Two cases of threatening letters with their accompanying envelopes were received to the Division of Forensic Identification unit of the Israel Police. The envelopes, including the stamps, and the letters were initially examined for latent fingerprints by the DFO reagent, known to cause degradation of DNA. Although no latent fingerprints could be visualized on any of the items, the biology laboratory using organic DNA extraction, was successful in defining genetic profiles from all the items employing six STR loci, even after treatment with DFO. In a controlled experiment, a known donor attached a stamp, by licking, to an envelope. This item was treated with DFO and then profiled using STR loci. The results showed that previous DFO treatment on the control stamp before DNA analysis had no negative effects on obtaining the DNA profile of the known donor using STR loci.     

Using previous DNA casework data to aid decision making in the process of DNA profile interpretation

In this study, a DNA decision support tool was developed. With this tool we aim to gain insight in what actions are performed with which (types of) DNA profiles in casework, to improve decision making by DNA experts in future cases.     

Interpretation of repeat measurement DNA evidence allowing for multiple contributors and population substructure

Due to the circumstances in some forensic cases, very small amounts of DNA (<100 pg) may be obtained. This, in turn, may affect the reliability of the PCR process, and so it may be advisable to repeat the amplification process for confirmatory purposes. Gill et al. [Forensic Sci. Int. 112 (2000) 17] proposed a method for the statistical evaluation of the PCR replicate information. In this paper we formalize the method proposed by Gill et al. [Forensic Sci. Int. 112 (2000) 17], and extend it to allow for cases involving mixed stains and for population substructure.     

Study on the application of parent-of-origin specific DNA methylation markers to forensic genetics

In paternity test, especially in motherless cases, the allele inherited from father (obligatory gene, OG) often cannot be determined. The paternity exclusion probability (PE) of a genetic marker is reduced considerably. Therefore, it is necessary to develop a new technique, by which the parental origin of alleles can be determined without genealogical analysis. In this paper, we explored the possibility of using parent-of-origin specific DNA methylation markers to determine the parental origin of alleles, choosing the imprinted single nucleotide polymorphism (SNP) locus rs220028 (A/G) as a model system. We typed the SNP by mutagenically separated PCR (MS-PCR). The frequencies of alleles were A = 0.5085, G = 0.4915; the unbiased heterozygosity was 0.5020. In order to discriminate between the maternal allele and paternal allele, post-digestion MS-PCR, a novel PCR based methylation analysis and SNP typing technique was developed and performed on 18 heterozygous children, and the methylated maternal allele was detected specifically. As a pilot study on the use of epigenetic markers in forensic genetics, our results demonstrated the feasibility of using parent-of-origin specific DNA methylation markers to determine the parental origin of alleles.