Y-STR DNA amplification as biological evidence in sexually assaulted female victims with no cytological detection of spermatozoa

DNA Profiling in Human Identification: From Past to Present

Forensic DNA typing has been widely accepted in the courts all over the world. This is because DNA profiling is a very powerful tool to identify individuals on the basis of their unique genetic makeup. DNA evidence is capable of not only identifying the presence of specific biospecimens in a crime scene, but it is also used to exonerate suspects who are innocent of a crime. Technological advancements in DNA profiling, including the development of validated kits and statistical methods have made this tool to be more precise in forensic investigations. Therefore, validated combined DNA index system (CODIS) short tandem repeats (STRs) kits which require very small amount of DNA, coupled with real-time polymerase chain reaction (PCR) and the statistical strengths are used routinely to identify human remains, establish paternity or to match suspected crime scene biospecimens. The road to modern DNA profiling has been long, and it has taken scientists decades of work and fine tuning to develop highly accurate testing and analyses that are used today. This review will discuss the various DNA polymorphisms and their utility in human identity testing.

A novel co-amplification system for simultaneous amplification of 23 Y-STR and identification of spermatozoa

In alleged sexual assault cases, identification of the presence of spermatozoa at the crime scene, or on items of eventual significance, or associated with the body of the victim, is integral to the forensic investigation to support or refute the proposition that sexual act has occurred. A 3-plex MSRE-PCR (methylation-sensitive restriction enzyme-PCR) system has been developed previously to identify spermatozoa based on the presence or absence of DNA methylation. This assay showed that 0.1 ng of DNA from a semen extract was sufficient to identify the presence of spermatozoa even when there was excessively more DNA isolated from vaginal fluid than DNA from a semen extract (80 ng/0.1 ng) or a mix of the menstrual blood/semen DNA (5 ng/0.1 ng). In this study, we combine spermatozoa detection with co-amplification of 23 Y-STR loci. We perform standard validation steps to present a novel test that saves time and uses the same sample for both DNA typing and spermatozoa detection in the same reaction. The combined assay can identify Y-STR and spermatozoa simultaneously using just 0.1 ng semen DNA, even in the presence of 5 ng of DNA from a female (male/female:1/50). No other body fluid tested, such as saliva, gave a result for the presence of spermatozoa. A total of 9 non-probative forensic samples from 7 sexual assault cases were tested by this co-amplification system. In all cases, the same sperm-positive data were obtained, concordant with our previous study analyzed by only 3-plex MSRE-PCR, and the Y-STR results were also consistent with that analyzed by only PowerPlex® Y23 kit. The co-amplification will be beneficial for the limited samples in many criminal cases.

Characterizing Y-STRs in the Evaluation of Population Differentiation Using the Mean of Allele Frequency Difference between Populations

Y-chromosomal short tandem repeats (Y-STRs) are widely used in human research for the evaluation of population substructure or population differentiation. Previous studies show that several haplotype sets can be used for the evaluation of population differentiation. However, little is known about whether each Y-STR in these sets performs well during this procedure. In this study, a total of 20,927 haplotypes of a Yfiler Plus set were collected from 41 global populations. Different configurations were observed in multidimensional scaling (MDS) plots based on pairwise genetic distances evaluated using a Yfiler set and a Yfiler Plus set, respectively. Subsequently, 23 single-copy Y-STRs were characterized in the evaluation of population differentiation using the mean of allele frequency difference (mAFD) between populations. Our results indicated that DYS392 had the largest mAFD value (0.3802) and YGATAH4 had the smallest value (0.1845). On the whole, larger pairwise genetic distances could be obtained using the set with the top fifteen markers from these 23 single-copy Y-STRs, and clear clustering or separation of populations could be observed in the MDS plot in comparison with those using the set with the minimum fifteen markers. In conclusion, the mAFD value is reliable to characterize Y-STRs for efficiency in the evaluation of population differentiation.

Updated Guidelines for the Medical Assessment and Care of Children Who May Have Been Sexually Abused

The medical evaluation is an important part of the clinical and legal process when child sexual abuse is suspected. Practitioners who examine children need to be up to date on current recommendations regarding when, how, and by whom these evaluations should be conducted, as well as how the medical findings should be interpreted. A previously published article on guidelines for medical care for sexually abused children has been widely used by physicians, nurses, and nurse practitioners to inform practice guidelines in this field. Since 2007, when the article was published, new research has suggested changes in some of the guidelines and in the table that lists medical and laboratory findings in children evaluated for suspected sexual abuse and suggests how these findings should be interpreted with respect to sexual abuse. A group of specialists in child abuse pediatrics met in person and via online communication from 2011 through 2014 to review published research as well as recommendations from the Centers for Disease Control and Prevention and the American Academy of Pediatrics and to reach consensus on if and how the guidelines and approach to interpretation table should be updated. The revisions are based, when possible, on data from well-designed, unbiased studies published in high-ranking, peer-reviewed, scientific journals that were reviewed and vetted by the authors. When such studies were not available, recommendations were based on expert consensus.

Validation of a combined autosomal/Y-chromosomal STR approach for analyzing typical biological stains in sexual-assault cases

DNA testing is an established part of the investigation and prosecution of sexual assault. The primary purpose of DNA evidence is to identify a suspect and/or to demonstrate sexual contact. However, due to highly uneven proportions of female and male DNA in typical stains, routine autosomal analysis often fails to detect the DNA of the assailant. To evaluate the forensic efficiency of the combined application of autosomal and Y-chromosomal short tandem repeat (STR) markers, we present a large retrospective casework study of probative evidence collected in sexual-assault cases. We investigated up to 39 STR markers by testing combinations of the 16-locus NGMSElect kit with both the 23-locus PowerPlex Y23 and the 17-locus Yfiler kit. Using this dual approach we analyzed DNA extracts from 2077 biological stains collected in 287 cases over 30 months. To assess the outcome of the combined approach in comparison to stand-alone autosomal analysis we evaluated informative DNA profiles. Our investigation revealed that Y-STR analysis added up to 21% additional, highly informative (complete, single-source) profiles to the set of reportable autosomal STR profiles for typical stains collected in sexual-assault cases. Detection of multiple male contributors was approximately three times more likely with Y-chromosomal profiling than with autosomal STR profiling. In summary, 1/10 cases would have remained inconclusive (and could have been dismissed) if Y-STR analysis had been omitted from DNA profiling in sexual-assault cases.

Genetic polymorphism of 15 Y chromosomal STR loci and haplotypes of Henan Han population

We studied and established a DNA database of 15 Y-STRs (DYS438, DYS446, DYS391, DYS390, DYS458, DYS534, DYS426, DYS626, DYS504, DYS505, DYS576, DYS532, DYS594, DYS522, DYS540) in a population sample of 102 unrelated, healthy, male individuals of Henan Han population. Allelic frequencies and statistical parameters of Han population were calculated. Totally 90 alleles were observed, with the corresponding allelic frequencies ranging from 0.0098 to 0.9020. 102 haplotypes were found in the studied group, the haplotype diversity for 15 Y-STR loci was 1. The results of present study were valuable for human identification and paternity tests routine forensic applications in the region.

Detection of male DNA in the vaginal cavity after digital penetration using Y-chromosome short tandem repeats

In this study, useful genetic information from male donors was obtained on vaginal swabs taken from female volunteers after male digital vaginal penetration in a time frame relevant to a sexual assault investigation. Vaginal swabs were collected from eight volunteers at intervals of 1, 6, 12, 24, and 72 hours after digital vaginal penetration. DNA was extracted from collected swabs and subsequently genotyped using a commercially available Y-chromosome short tandem repeats (Y-STR) multiplex kit. Fifty-eight vaginal swabs were collected and analyzed in the study. Composite Y-STR profiles from all combined volunteers showed that 85% of all possible alleles were detected at the 1-hour interval, 77% of all possible alleles were detected at the 6-hour interval, 73% of all possible alleles were detected at the 12-hour interval, 66% of all possible alleles were detected at the 24-hour time interval, and 71% of all possible alleles were detected at 72 hours after digital vaginal penetration. Results indicate that a viable possibility exists that probative Y-STR profiles, useful for investigative purposes, can be obtained from vaginal swabs taken from subjects exposed to digital penetration at time intervals up to 72 hours postpenetration.

Y-STR analysis of digital and/or penile penetration cases with no detected spermatozoa

This forensic casework trial involved Yfiler(®) testing samples from 47 digital and/or penile penetration cases where the medical examination had occurred within 48h of the alleged incident and no spermatozoa had been detected following Sperm Elution(©). 30% of these cases yielded at least one Y-STR profile comprising three or more alleles per profile and 21% yielded at least one Y-STR profile of ten or more alleles per profile. This trial further investigated the persistence of male DNA in different case types, the location of samples submitted for testing and whether samples from different locations benefit from being combined prior to testing. The data supports the use of Y-STR profiling to provide scientific evidence to investigate whether the alleged sexual activity had occurred as well as to obtain probative evidence in spermatozoa negative penetration cases.

Recent advances in forensic genetics

Like many applications of molecular diagnostics, the field of forensic biology is undergoing a phase of expansion and diversification. The growth of forensic DNA databases and adoption of sophisticated analytical methods have catalyzed this increasing role. The range of molecular markers exploited in the fight against crime is beginning to increase too, and genes implying personal or physical characteristics are emerging in the research literature. However, the operational context of forensic biology is unlike many other fields of science. Harmonizing technological breakthroughs with the requirements of law enforcement agencies and the complexities of the legal system is an added challenge and one which evokes ongoing debate. This review examines the current status of this dynamic and important application of modern genetics.

Human migration, diversity and disease association: a convergent role of established and emerging DNA markers

With the gradual development of intelligence, human got curious to know his origin and evolutionary background. Historical statements and anthropological findings were his primary tool for solving the puzzles of his own origin, until came the golden era of molecular markers which took no time to prove it's excellence in unveiling answers to the questions regarding the migration pattern of human across different geographical regions. As a bonus these markers proved very much beneficial in solving criminal offenses and in understanding the etiology of many dreaded diseases and to design their prevention. In this review, we have aimed to throw light on some of the promising molecular markers which are very much in application now-a-days for not only understanding the evolutionary background and ancient migratory routes of humans but also in the field of forensics and human health.

Forensic expertise and judicial practice: evidence or proof?

RATIONALE, AIMS AND OBJECTIVES

This study presents for discussion the possibility of adopting a hypothesis of absolute truth in forensic serology and DNA testing of biological traces, taking into account identification probability, which is usually assumed to be greater than 95%. Can this be so? Established identity and mathematically calculated probability below this rate is not false because it depends on the sensitivity of the method, the possible number of variations and theoretical combinations. The result from a study can be considered a 100% identification result only if this study takes account of absolutely all quantitative criteria that characterize it.

METHODS

Under the conditions of continually evolving theory and practice, and the introduction of modified and expanded methods for analysis of biological materials, it may therefore be asked which method considers 'everything'. Although this finding is nihilistic, it reflects a truth, which we can define as absolute. In forensic practice, research methods assumed to be orientation ones and others identified as evidence for the presence of biological traces on objects carriers, are routinely employed.

RESULTS

Based on several groups of forensic cases, the question of the limits of precision and relevance of the results to the categories of evidence and proof is formulated and discussed. Three groups of expertise cases are presented, which warrant discussion: (i) a study of condoms with genetic material on both sides: female DNA on the outer surface and male DNA on the inner. What is this evidence for or what does it prove?; (ii) a study of cigarette butts found at a crime scene with deposited cellular material from the offender. Is this evidence or proof?; (iii) the DNA expertise in the case of controversial parental origin or the vasectomy of the man referred to as the father.

CONCLUSIONS

What will the court choose as proof or is it a case of mutually exclusive evidence? Such considerations lead to the dilemma: 'evidence or proof'?

The utility of Y-STR profiling in four-, six- and eight-day postcoital vaginal swabs

Y-STR profiles using the Promega PowerPlex(®) Y system were attempted on multiple vaginal swabs collected at four, six and eight days after intercourse from female partners of 11 couples. At four days postcoitus, full composite profiles (where swabs yielded confirmed alleles at all 11 loci) were obtained for five of the 11 couples and 78% of all possible alleles summed for all couples were confirmed (able to be duplicated in different swabs). Results for composite profiles for all couples taken at six days after intercourse showed that 53% of all alleles summed for all couples were confirmed. Only one couple yielded a full composite profile at six days after intercourse. Composite profiles from swabs taken at eight days after intercourse for all couples confirmed only 44% of all possible alleles summed for all couples. At eight days postcoitus, no couple yielded a full composite profile and the largest number of confirmed alleles for any couple was eight. However, one of 44 individual swabs taken from all couples combined at eight days postcoitus yielded a 10-locus profile. Composite partial profiles from the eight-day postcoital set with confirmed results at a minimum of five loci (8 of 11 couples) yielded haplotype frequencies from 0.000323 to 0.125862 using the Y chromosome haplotype reference database, suggesting that meaningful Y-STR information can still be obtained at much extended postcoital intervals.

The forensic nursing in sexual assaults: the immunochemical diagnosis and prevention of its adverse effects

Sexual assault was a ubiquitous and serious problem in our society. The world's care centers and forensic associations, which were at the forefront of scientific research in sexual assaults, discussed the role of the Forensic Nursing in their early diagnosis and their prevention, but little has been written in literature regarding their appropriate management. This article focuses on the immunochemical laboratory investigation in diagnosis and prevention of its adverse effects in sexual assaults and the role of the Forensic Nursing played in this task. After a careful reading of all the material received from many of the care centers and the associations contacted, a Forensic Nursing Examination Program, with specific immunochemical address, is identified.

[Polymorphism of 17 Y-STR loci in Shanxi Han population and genetic relationship with 13 populations]

To investigate the genetic polymorphisms of 17 Y-chromosomal short tandem repeats (Y-STR) loci in Shanxi Han population and to explore their forensic application values and genetic relationship with neighboring populations, 17 Y-STR in 222 unrelated healthy Shanxi Han individuals were amplified with Y-filerTM System, and the PCR products were detected with 3130 Genetic Aanalyzer. The allele frequencies and haplotype diversity were calculated. Y-STR data of another 13 populations were collected from publications. Cluster analysis and phylogenic trees were applied to show the genetic distance among the populations. As a result, a total of 219 haplotypes were identified, and the observed haplotypes diversity value was 0.9999. The gene diversity values (GD) for each locus ranged from 0.3894 (DYS391) to 0.9755 (DYS385a/b). Comparing with 13 populations, the genetic distance between Shanxi and Jihei Han populations was the smallest (0.0001), while the genetic distance between Shanxi and Taiwan population was the largest (0.0152). The phylogenetic tree was similar to the results of clustering analysis. Multiplex detection of the 17 Y-STR loci revealed a highly polymorphic genetic distribution, which would be very powerful for establishing a Y-STR database, for population genetics and forensic practice.

The recovery and persistence of salivary DNA on human skin

Salivary DNA is encountered in many crimes, such as sexual assaults and murders. In this study, saliva from three male donors was deposited on the skin of three female recipients. The amount of male salivary DNA remaining on the female skin was measured over a 96-h period using the Quantifiler™ Y Human Male DNA Quantification Kit. In eight of the nine experiments, a full male DNA profile matching the donor was obtained even after 96 h. In addition, the study showed that the concentration of salivary DNA varied from donor to donor and from day to day. The efficiency of two recovery methods, wet and dry swabbing and minitaping, was compared. The results indicate the tapelift method gave higher DNA recovery. This study also examined the secondary transfer of salivary DNA from skin to fabrics. Cotton and polyester give higher DNA transfer than leather.

[Polymorphism of 22 Y-STR loci in Guangdong Han population and genetic relationship with 12 populations]

To investigate the genetic polymorphisms of 22 Y-chromosomal short tandem repeats(STR) loci in Guangdong Han population, and to evaluate their forensic application values and genetic relationships with 12 other populations. These Y-STR loci (DYS19, DYS389/, DYS390, DYS391, DYS392, DYS393, DYS385, DYS437, DYS438, DYS439, DYS461, DYS481, DYS504, DYS505, DYS508, DYS533, DYS576, DYS588, DYS607, DYS634, and DYS643) were analyzed in 216 unrelated healthy Guangdong Han individuals by three multiplex PCR systems including the PowerPlex Y System. Cluster analysis and phylogenic trees were applied to show the genetic distance among the populations. As a result, a total of 214 haplotypes were identified and the overall haplotype diversity for the 22 Y-STR loci was 0.9999. The gene diversity values (GD) for each locus ranged from 0.3299 (DYS634) to 0.9425 (DYS385). Comparing with 12 other populations, the genetic distance between Guangdong and Chaoshan Han population was the smallest (-0.0030), while that between Guangdong and Northeast Han Chinese was the largest (0.0195). The phylogenetic tree was similar to the results of clustering analysis. Multiplex detection of the 22 Y-STR loci revealed a highly polymorphic genetic distribution, which would be very powerful for establishing a Y-STR database, for population genetics and forensic practice.

[Polymorphism analysis of 11 Y-STR loci in Manchu population and genetic relationships with 16 populations]

To investigate the genetic polymorphisms of 11 Y-chromosomal short tandem repeats(STR) loci in Manchu population, and to evaluate their forensic application values and genetic relationships with 16 other populations of China, 11 Y-STR loci in 203 unrelated Manchu individuals in Liaoning were amplified with PowerPlex Y System, and the PCR products were analyzed by 310 Genetic Analyzer. Cluster analysis and phylogenic trees were applied to show the genetic distance among the populations. As a result, a total of 189 haplotypes were identified and the overall haplotypes diversity for the 11 Y-STR loci was 0.9991. The gene diversity values (GD) for each locus ranged from 0.4594 (DYS391) to 0.9258 (DYS385a/b). Comparing with 16 populations, genetic distance between Manchu and Northeast Han population was the smallest(0.0015), while genetic distance between Man and Uygur ethnic the largest(0.1485). The phylogenetic tree was similar to the results of clustering analysis. The genetic distribution of 11 Y-STR loci in Liaoning Manchu population showed favorable polymorphisms, and was thus suitable for forensic identification and paternity testing in local area. The study of genetic diversity among different populations is useful for the research of their origins, migrations and their relationships.

Haplotypes of 20 Y-chromosomal STRs in a population sample from southeast China (Chaoshan area)

In this study, 20 Y-specific short tandem repeat (STR) loci (DYS434, Y-GATA-A10, Y-GATA-H4, DYS438, DYS439, DYS443, DYS444, DYS446, DYS447, DYS448, DYS456, DYS458, DYS460, DYS520, DYS531, DYS557, DYS622, DYS630, DYS635(Y-GATA-C4), and DYS709) were analyzed in 158 unrelated healthy men from southeast China by three fluorescence-labeled multiplex polymerase chain reaction systems. The Y-STR multiplexes developed have followed the published nomenclature and International Society for Forensic Genetics (ISFG) guidelines for STR analysis. Gene diversity ranged from 0.2506 at DYS434 to 0.8034 at DYS447. A total of 157 different haplotypes were observed, and among these, 156 were unique, while 1 was found two times. The haplotype diversity value calculated from all 20 loci combined was 0.9997, which is informative. Furthermore, 80 father-son pairs, previously confirmed by autosomal STR analysis, were typed using the same 20 Y-STR loci, and four mutation events were identified at the Y-GATA-H4, DYS439, DYS456, and DYS458 loci, giving an average mutation rate of 0.25% per locus per generation (95% confidence interval 0.09-0.54). These results including the haplotype data at 20 Y-STR loci would enrich Chinese genetic informational resources and provide useful information in forensic practice.

Investigations of the Y chromosome, male founder structure and YSTR mutation rates in the Old Order Amish

OBJECTIVES

Using Y chromosome short tandem repeat (YSTR) genotypes, (1) evaluate the accuracy and completeness of the Lancaster County Old Order Amish (OOA) genealogical records and (2) estimate YSTR mutation rates.

METHODS

Nine YSTR markers were genotyped in 739 Old Order Amish males who participated in several ongoing genetic studies of complex traits and could be connected into one of 28 all-male lineage pedigrees constructed using the Anabaptist Genealogy Database and the query software Ped-Hunter. A putative founder YSTR haplotype was constructed for each pedigree, and observed and inferred father-son transmissions were used to estimate YSTR mutation rates.

RESULTS

We inferred 27 distinct founder Y chromosome haplotypes in the 28 male lineages, which encompassed 27 surnames accounting for 98% of Lancaster OOA households. Nearly all deviations from founder haplotypes were consistent with mutation events rather than errors. The estimated marker-specific mutation rates ranged from 0 to 1.09% (average 0.33% using up to 283 observed meioses only and 0.28% using up to 1,232 observed and inferred meioses combined).

CONCLUSIONS

These data confirm the accuracy and completeness of the male lineage portion of the Anabaptist Genealogy Database and contribute mutation rate estimates for several commonly used Y chromosome STR markers.

Y-STRs in forensic medicine: DNA analysis in semen samples of azoospermic individuals

The incidence of rape has increased, especially in metropolitan areas, such as the city of São Paulo. In Brazil, studies about it have shown that the majority of this type of crime is committed by the relatives and persons close to the victim. This has made the crime more difficult to be denounced, as only 10% of the cases are reported to competent police authorities. Usually, cytological exams are carried out in sex crime investigations. The difficulty in showing the presence of spermatozoa is frequent, but it does not exclude the presence of male DNA. The absence of spermatozoa in material collected from rape victims can be due to several factors, including the fact that the agressor suffers from azoospermia. This condition can be the result of a successful vasectomy. As the majority of DNA in the ejaculation sample is from spermatozoa, there is much less DNA to be analyzed. This study presents the application of Y-STRs (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, and DYS393) in DNA analysis of sperm samples from 105 vasectomized men. The study demonstrated a great variation in DNA concentration. DNA extraction and amplification was possible in all sperm samples even in the absence of spermatozoa. The same profile was observed, for each individual, from DNA extracted from blood, pre- and postvasectomy semen samples. The use of markers specific for Y chromosome in sex crime cases, especially in the absence of spermatozoa, is very important, mainly because in most situations there is a small quantity of the agressor's DNA in the medium and a large quantity of the victim's DNA.

Vaginal douching and intimate partner violence: is there an association?

OBJECTIVE

This study tests the hypothesis that vaginal douching among women of reproductive age is associated with exposure to intimate partner violence (IPV).

METHODS

The data source is a cross-sectional population-based sample of 2,002 women ages 18-45 in the Central Pennsylvania Women's Health Study. The survey included measures of IPV, douching behavior, and relevant sociodemographic and health-related covariates.

FINDINGS

Six percent of the sample reported experiencing any type of IPV in the past year, and 23% reported douching in the past year. IPV is significantly associated with douching after controlling for sociodemographic and health-related covariates. This finding holds for women with and without current reproductive capacity.

CONCLUSIONS

This is the first study to identify an association between vaginal douching and IPV. Because vaginal douching is a risk factor for sexually transmitted infections, bacterial vaginosis, and adverse pregnancy outcomes, the findings could have important implications for prevention. Further research is needed to identify the reasons why women who have been exposed to IPV are more likely to douche.

Y-chromosomal STR haplotypes in a Northeast Italian population sample using 17plex loci PCR assay

One hundred fifty-five unrelated, autochthonous healthy males from Northeast Italy were typed for the 17 Y-chromosome short tandem repeat (STR) (Y-STR) loci DYS456, DYS389I, DYS390, DYS389II, DYS458, DYS19, DYS385, DYS393, DYS391, DYS439, DYS635, DYS392, Y GATA H4, DYS437, DYS438, DYS448 using the AmpFLSTR Yfiler polymerase chain reaction amplification kit. A total of 153 different haplotypes were observed, and among these, 151 were unique, while 2 were found two times. The overall haplotype diversity was 0.9997. Furthermore, 50 father-son pairs, previously confirmed by autosomal STR analysis, were typed using the same set of 17 Y-STR loci, and, among 850 allele transfers, three mutation events were identified, giving an average mutation rate of 3.53 x 10(-3) per locus per generation (95% confidence interval 0.73-1.03).

Whole genome amplification strategy for forensic genetic analysis using single or few cell equivalents of genomic DNA

Evidentiary items sometimes contain an insufficient quantity of DNA for routine forensic genetic analysis. These so-called low copy number DNA samples (< 100 pg of genomic DNA) often fall below the sensitivity limitations of routine DNA analysis methods. Theoretically, one way of making such intractable samples amenable to analysis would be to increase the number of starting genomes available for subsequent STR (short tandem repeat) analysis by a whole genome amplification strategy (WGA). Although numerous studies employing WGA have focused primarily on clinical applications, few in-depth studies have been conducted to evaluate the potential usefulness of these methods in forensic casework. After an initial evaluation of existing methods, a modified WGA strategy was developed that appears to have utility for low copy number forensic casework specimens. The method employs a slight, but important, modification of the "improved primer extension preamplification PCR" method (I-PEP-PCR), which we term mIPEP (modified-I-PEP-PCR). Complete autosomal STR and Y-STR (Y chromosome short tandem repeat) profiles were routinely obtained with 5 pg of template DNA, which is equivalent to 1-2 diploid cells. Remarkably, partial Y- and autosomal STR profiles were obtained from mIPEP-treated DNA recovered from bloodstains exposed to the outside environment for 1 year whereas non-mIPEP-treated samples did not produce profiles. STR profiles were obtained from contact DNA from single dermal ridge fingerprints when the DNA was subjected to prior mIPEP amplification but not when the mIPEP step was omitted.

Digoxigenin labelling and laser capture microdissection of male cells

Laser capture microdissection (LMD) is a relatively new technique for the isolation of single cells. The application in forensic investigations has become more and more widespread, especially to select spermatozoa out of mixtures with vaginal cells. In particular in cases with low numbers of sperm it could be profitable to isolate all male cells (e.g. sperm and male epithelial cells) instead of focussing on the sperm only. Therefore, the specific labelling and detection of the male cells in a male/female cell mixture is necessary. In order to label all cells carrying a Y-chromosome we used a digoxigenin labelled chromosome Y hybridisation probe (Q Biogen). The stained cells were isolated with the SL microCut LMD system from Molecular Machines & Industries AG (MMI). At least ten diploid male cells were required to obtain a partial STR profile, with 20 cells, a full profile could be obtained.

Y-STR analysis for detection and objective confirmation of child sexual abuse

We evaluated 26 child sexual assault cases for the incorporation of Y-STR screening in the routine detection and objective confirmation of sexual contact between the child victim and the perpetrator. Various samples, e.g. vaginal or anal swabs from patients aged 2-17 years old (25 females, 1 male), were collected 6-72 h after the incident. Due to the limited amounts of DNA in these samples, total DNA was extracted using a one-step procedure and screened with autosomal STRs to detect signs of a victim-assailant DNA mixture and with Y-STRs for assailant DNA. Autosomal STRs failed to give signs of victim-assailant DNA mixtures while Y-STRs were detected in 24 of the 26 cases corresponding to a success rate of 92.3%. With the possible presence of both male sperm and/or male epithelial cells in forensic evidence, Y-STR DNA markers were detected regardless of external ejaculation, microscopic detection of sperm and with post-coital intervals of up to 72 h. While only partial profiles were generated owing to low quantities of male DNA present, Y-STR screening results can serve as objective evidence of sexual contact in child sexual abuse cases involving victims who do not have any previous sexual history. This type of evidence can corroborate child victim testimony and spare the child victim from further trauma caused by prolonged forensic investigations and court proceedings. Alternatively, Y-STR screening can provide objective proof of non-involvement of an accused with the victim.

Novel Y-STR typing strategies reveal the genetic profile of the semen donor in extended interval post-coital cervicovaginal samples

For a variety of reasons, some victims of sexual assault provide vaginal samples more than 24-36 h after the incident. In these cases, the ability to obtain an autosomal STR profile of the semen donor from the living victim diminishes rapidly as the post-coital interval is extended. We have used a number of carefully selected Y-STR loci in a variety of multiplex or monoplex formats to extend the post-coital interval from which a genetic profile of the semen donor can be obtained. The proposed Y-STR typing strategies enable the routine detection of the male donor Y-STR haplotype in cervicovaginal samples recovered up to 4 days post-coitus. We attribute our success to a number of factors that significantly improve the sensitivity and specificity of the analysis. Firstly, we utilize a subset of Y-STR loci that have been carefully selected for their superior performance under stressed conditions in both multiplex and monoplex formats. Specifically these loci function with low copy number templates in the presence of a vast excess of potentially confounding female DNA. Secondly, sperm and non-sperm DNA is co-extracted without a differential extraction process to prevent the unnecessary loss of the small number of structurally fragile sperm remaining in the cervicovaginal tract several days after intercourse. Thirdly, low copy number detection is facilitated by increasing the cycle number to 34-35 cycles and by the ability to input up to 450 ng of co-extracted sperm/non-sperm DNA into the PCR reaction without the appearance of confounding female artifacts. Lastly, the proper collection of post-coital cervicovaginal samples, instead of the lower or mid-vaginal tract samples often taken, is required for optimal recovery of sperm for analysis. In this report we demonstrate that our previously described 19 Y-STR loci systems (MPI and MPII) permit a reliable high resolution haplotype determination of the semen donor in cervicovaginal samples taken up to 48 h after intercourse. However, as the post-coital interval is extended further, dramatic loss of signal is observed and haplotype determination of the male donor is no longer possible with MPI and MPII. Nonetheless, subsets of these 19 loci (MPA and MPB) have been developed specifically to detect the male haplotype in samples recovered 4 days after intercourse. Thus, it is possible to derive an 11-19 locus Y-STR profile of the semen donor in cervicovaginal samples recovered 2-4 days after intercourse.