Results of the 2008 Colombian paternity testing quality control exercise

The Reference National Laboratory, Genes Ltda, designated by the Commission of Accreditation and Alertness created by Law 721 of 2001 of Republic of Colombia, organized and coordinated the Quality Control Exercise of 2008 for laboratories undertaking paternity and maternity tests with DNA markers. The Quality Control Exercise included both practical and theoretical exercises. For the practical exercise, three blood samples in FTA Classic Card were sent to each participating laboratory to be genotyped for DNA markers using the routine methodologies in their laboratories. For the theoretical exercise, it was asked to the participating laboratories to calculate the partial and final paternity indexes based on two genetic profiles of an alleged biological father and his son. Allele frequencies were made available to the participants, as well as Y chromosome haplotype database. A total of 12 laboratories have participated with data from 57 STRs, including autosomal and sex chromosome markers. Consensus was found in 37 STRs, 21 in autosomes and 16 Y chromosome linked. The rate of reporting errors was 3.1% (concentrated in just one laboratory). The theoretical exercise had consensus.     

Development of two new Mini-STR multiplex assay for typing archival Bouin's fluid-fixed paraffin-embedded tissues

Short amplicon autosomal short tandem repeat (Mini-STR) assay has proved to be a highly useful tool in forensic applications, especially for highly degraded DNA samples that typically result in partial profiles and total loss of information from regular STR amplicons.In this study two new quadruplex systems were designed to get nuclear DNA profile from degraded forensic casework samples. In order to obtain PCR products less than 120 bp in size, primer pairs of eight STR markers, included in available commercially multiplex PCR kits, were redesigned and assembled in two PCR-multiplexes: D8S1179, D3S1358, TPOX, D16S539 and CSF1P0, TH01, D13S317, D5S818.After validation, these two Mini-STR quadruplex were employed in paternity testing case that involved DNA extraction from archival postmortem Bouin's fluid-fixed paraffin-embedded tissue where commercial kit yielded low success. The results obtained with the present Mini-STR PCR-multiplexes proved clearly demonstrating their usefulness in analyzing degraded DNA samples.     

Female criminals—It's not always the offender!

Numerous crimes (including murder), all having a common denominator, occurred in Germany and Austria between 1993 and 2009. All of these cases presented with identical female DNA traces being found at the crime scene. The crimes committed differed markedly, as did the suspects involved, which were of varied origin. Many of these cases could be solved. However, none of the suspects could identify an involved female. Fourteen of these cases (including one murder) occurred in Upper Austria.A special task force of the Austrian police, together with the Institute of Legal Medicine in Salzburg, began systematically searching for errors in the investigative process after the cases became more and more incoherent and nebulous. In the end, the DNA trace evidence was shown to be contaminated. A woman involved in the manufacture of the cotton swabs turned out to be the source of the female DNA profile.Following this, several products of other manufacturers were tested for contamination with DNA. It was noted that cotton swabs which had been sterilised with radiation were often contaminated. As a result, it is recommended that the manufacturing process, as well as the products themselves used in collection of DNA trace evidence, should be re-evaluated with the emphasis on preventing contamination.     

Trace DNA success rates relating to volume crime offences

In this study, 252 trace DNA samples (from handled surfaces) from 201 burglary, robbery and drugs cases were compiled to assess success rates and to interpret the value of trace DNA evidence in volume crime investigations. The average amount of DNA recovered from the trace DNA samples collected was 1.7 ng. Full or major (12 or more alleles) profiles were recovered from 14% of samples. Samples from firearms and burglary points of entry were the least successful. Mixtures were recovered from 21% of samples, presenting a case for the collection of more elimination profiles to enable more samples to be used for database purposes. The research highlighted the difficulties in collecting data relating to the success rates of samples. Computerised automation of this process would be extremely beneficial in the assistance of policy development, method application, training, and investigative usefulness.     

Genotyping of DNA samples under adverse conditions of Low Copy Number—LCN (formolisados tissue samples and embedded in paraffin)

This paper aims to describe and evaluate a protocol for extraction of DNA (deoxyribonucleic acid) in formalinized tissues and embedded in paraffin for forensics genetic analysis. In outline the method is the removal of paraffin with an organic solvent in 0.3–0.5 mg of the sample of the tissue under study, followed by removal of formaldehyde, rehydration and soon after the extraction of genomic DNA. The extraction is achieved through the stages of cellular lysis, enzymatic digestion of proteins and DNA precipitation in ethanol medium. With the research we can conclude that even when the DNA is present in small quantities in conditions of extreme difficulties in its extraction, as formalinized tissues and embedded in paraffin, the technique of optimizing the extraction of DNA used both to organic extraction as Chelex, for use in the polymerase chain reaction (PCR), and possible the investigation of different samples of human tissue, biological samples, or was obtained under the conditions tested, a DNA with good quality and concentration. The samples were amplified for the mini-STRs loci using the product marketed in multilocus, using a methodology recommended by the supplier and validated for analysis of forensic DNA. Commercial kit was used MiniFiler from Applied Biosystems. The DNA fragments amplified by PCR showed that the extracted DNA had good amplification.     

A new approach in the identification of degraded paternity samples

DNA extraction from bone is an important issue particularly in paternity cases when bones are the only remaining material to obtain and analyze DNA. The difficulties arising from bacterial damages, taphonomic factors and diagenesis might negatively affect the extraction and the amplification of DNA. This makes the laboratory procedure a hard and time-consuming process, and the analysis can fail. Analyzing mini-STRs in this type of degraded samples is highly recommended. In this study a new extraction technique was carried on bone samples which were then typed for mini-STRs. The aim was to differentiate two genetically related skeletons found in the same familial grave for a paternity test. The analysis revealed that this new extraction technique along with mini-STR analysis can properly be an effective way to obtain and analyze DNA in bones in the field of forensic sciences.     

降解生物检材DNA分析研究新进展

在法医检案过程中,如何从降解生物检材中获得正确的DNA分型是法医学界的一个难题.本文对降解生物检材DNA分析研究取得的新进展进行综述,从检案的各个环节出发对近年来提高DNA分型成功率的方法和技术进行了详细介绍,例如新型遗传标记的开发和二代测序技术的应用等.希望为降解检材的分析提供新的思考和方法.     

Recovery of Latent Fingerprints and DNA on Human Skin*

Abstract: The project “Latent Fingerprints and DNA on Human Skin” was the first systematic research in Europe dealing with detection of fingerprints and DNA left by offenders on the skin of corpses. One thousand samples gave results that allow general statements on the materials and methods used. The tests were carried out according to a uniform trial structure. Fingerprints were deposited by natural donors on corpses. The latent fingerprints were treated with magnetic powder or black fingerprint powder. Afterward, they were lifted with silicone casting material (Isomark^®) or gelatine foil. All lifts were swabbed to recover DNA. It was possible to visualize comparable and identifiable fingerprints on the skin of corpses (16%). In the same categories, magnetic powder (18.4%) yielded better results than black fingerprint powder (13.6%). The number of comparable and identifiable fingerprints decreased on the lifts (12.7%). Isomark^® (14.9%) was the better lifting material in comparison with gelatine foil (10.1%). In one‐third of the samples, DNA could be extracted from the powdered and lifted latents. Black fingerprint powder delivered the better result with a rate of 2.2% for full DNA profiles and profiles useful for exclusion in comparison with 1.8% for the magnetic powder traces. Isomark^® (3.1%) yielded better results than gelatine foil (0.6%).     

DNA数据库建设中批量样本直接扩增检验法的应用

目的研究批量样本直接扩增法在DNA数据库建设中的应用。方法打孔机打取血滤纸600份,剪取芝麻大小的口腔拭子300份,放入96孔扩增板,加入扩增试剂后直接扩增,并对其中200份血滤纸用磁珠法,100份口腔拭子用96孔板Chelex-100法,经DNA提取后扩增检验进行比较。结果血滤纸采用直接扩增法及磁珠法STR检测成功率均为100%;口腔拭子采用直接扩增法的成功率为95%,采用96孔板Chelex-100法的成功率为94%。结论血滤纸和口腔拭子通过直接扩增均能获得很好的DNA分型结果,该方法省时省力,可用于DNA数据库建设。     

Heteroplasmy in Hair: Study of Mitochondrial DNA Third Hypervariable Region in Hair and Blood Samples*†

Abstract: Mitochondrial DNA (mtDNA) analysis has proved useful for forensic identification especially in cases where nuclear DNA is not available, such as with hair evidence. Heteroplasmy, the presence of more than one type of mtDNA in one individual, is a common situation often reported in the first and second mtDNA hypervariable regions (HV1/HV2), particularly in hair samples. However, there is no data about heteroplasmy frequency in the third mtDNA hypervariable region (HV3). To investigate possible heteroplasmy hotspots, HV3 from hair and blood samples of 100 individuals were sequenced and compared. No point heteroplasmy was observed, but length heteroplasmy was, both in C‐stretch and CA repeat. To observe which CA “alleles” were present in each tissue, PCR products were cloned and re‐sequenced. However, no variation among CA alleles was observed. Regarding forensic practice, we conclude that point heteroplasmy in HV3 is not as frequent as in the HV1/HV2.