Prevalence and persistence of foreign DNA beneath fingernails

Fingernail scrapings and clippings are routinely examined for the presence of foreign DNA profiles in forensic casework where the case history suggests their evidentiary relevance. In order to better understand the significance of these findings, casework results from the Centre of Forensic Sciences (CFS) were analyzed and several controlled studies were conducted. In an analysis of casework data (n=265), 33% of fingernail samples contained a foreign source of DNA, 63% of which were detected at 5 or more STR loci. In a sampling of fingernails from the general population (n=178), 19% contained a foreign source of DNA, 35% of which were detected at 5 or more STR loci. In a study involving deliberate scratching of another individual (n=30), 33% of individuals had a foreign DNA profile beneath their fingernails from which the person they scratched could not be excluded as the source; however when sampling occurred ≈ 6 h after the scratching event, only 7% retained the foreign DNA. This research suggests the incidence of foreign DNA profiles beneath fingernails in the general population is low but, when present, the majority is of limited significance and tends not to persist for an extensive period of time. These data are provided to assist the forensic analyst when providing his or her opinion as to the relevance of foreign DNA present under fingernails.     

Zwei Beispiele zur Anwendbarkeit Y-chromosomaler DNA-Polymorphismen in der forensischen Spurenanalytik

Two cases where DNA typing has been carried out for stain analysis are described. In both cases Y chromosomal STR systems have been used in combination with autosomal STR systems. In the first case the DNA from the fingernails of a female victim with skin particles of the male murderer was typed. The male DNA in this mixture of male and female DNA could be typed. The excess of female DNA in the samples did not distrub the PCR reaction of Y-chromosomal systems. In the second case several body parts could be identified to belong to a single male person. The typing of the suspect’s DNA did not give any information because of a family relationship. Different kinds of stains have been analysed with DYS 389 I/II, DYS 390, DYS 391, DYS 392 DYS 393 and DYS19. Two multiplex PCR reactions were carried out to save time and stain material. Although the Y-chromosomal systems are not as polymorphic as autosomal STR systems the analysis of combined haplotypes can give additional information in forensic casework.     

Criminal anticipation of DNA investigations resulting in mutilation of a corpse

A corpse of a female was found in her apartment in a state of advanced putrefaction. Both hands were amputated, the external genitals were excised and the body parts had been removed from the scene. The subsequent investigations proved that the body parts had been severed post mortem. The cause of death was determined to be manual strangulation. A 33-year-old man later confessed that he had strangled the victim 9 days prior to discovery of the body and that he had had sexual intercourse post mortem. According to the confession, the rational motive for the subsequent mutilation was to eliminate biological stains (e.g. semen inside the vagina, epithelial cells below the fingernails from scratching) suitable for forensic DNA analysis. This constitutes a new type of defensive mutilation intended to prevent the identification of the perpetrator. An increase in the occurrence would be detrimental to the elucidation rate of homicides: in a total of 171 homicides investigated at this institute, DNA analysis of biological stains gave reliable evidence in 45 cases. Received: 26 February 1999 / Received in revised form: 15 July 1999     

A comparative study for the isolation of exogenous trace DNA from fingernails

Often fingernails from a victim or suspect involved in a physical assault, such as murder or sexual assault, are submitted to crime laboratories for DNA testing of foreign/exogenous biological material; however, very few studies have been conducted comparing the effectiveness of different sampling methods on the removal of foreign/exogenous DNA while minimizing the fingernail endogenous DNA. In this study three different sampling methods (swabbing, PBS soak, and PrepFiler® lysis buffer soak) were compared in order to identify one that minimizes the amount of endogenous DNA removed and maximizes the amount of foreign/exogenous male DNA removed. The samples were processed using the Tecan HIDEVO150 robot in order to reduce analyst time and the DNA mixtures were interpreted using the probabilistic genotyping software STRmix™. For each sampling method the quantity of male DNA, the mixture proportions, the number of foreign/exogenous male alleles detected, the amount of DNA degradation, and the discrimination power via the likelihood ratio obtained for the foreign/exogenous male DNA donor were determined and compared. The PrepFiler® lysis buffer soak and swabbing sampling methods appear to be equally effective at removing foreign/exogenous DNA from fingernails; however, the lysis buffer soak sampling method extracts more female endogenous DNA from the fingernail and the female DNA is degraded. Marginally higher likelihood ratios were obtained for the swab samples versus the PrepFiler® lysis buffer soak samples; therefore, it was determined that the swabbing sampling method was the best sampling method for the recovery of foreign exogenous DNA from fingernails while minimizing the amount of endogenous DNA removed.     

The prevalence of mixed DNA profiles in fingernail samples taken from individuals in the general population

The fingernail hyponychium is an isolated area where biological material may accumulate and can provide a valuable source of evidential material in police investigations. DNA transfer between the victim and suspect frequently occurs during violent crimes and in court there is often reasonable doubt that a mixed DNA profile in a fingernail sample has originated from the assault as the profile may be attributed to previous contact between the two individuals. The purpose of this study was to assess background levels of foreign DNA under the fingernails of individuals from the general population in order to provide data that may help to determine whether DNA transfer occurred during or prior to the assault. Fingernail swabs sampled from 100 volunteers were processed by Qiagen™ extraction and amplified using AMPFlSTR^® SGM Plus™ to obtain DNA profiles. Foreign DNA was detected in 13% of samples, with only 6% of these giving reportable mixed DNA profiles, suggesting the incidence of foreign DNA under the fingernails was low. A significant proportion of the mixed DNA profiles came from male donors; the majority had experienced physical contact within the 24 h time period prior to sampling.     

Effects of environmental conditions to which nails are exposed on DNA analysis of them

To investigate the feasibility of DNA analysis of nails taken from human remains after environmental exposure, we tested the quantity and quality of DNA that could be recovered from nails exposed to various conditions. We first investigated whether there is an inter- or intra-subject difference in the DNA content of nails using nails obtained from 333 volunteers. DNA content did not significantly differ between males and females, or between young and elderly groups. In addition, no statistically significant differences were observed among nail samples obtained from each finger of the same person. Then thumbnails of five volunteers were left in dried soil, wet soil, river water, sea water, distilled water or air for 3 months. Each nail sample was tested monthly for sex chromosome-specific repeats, ABO genotype, STRs (TH01, TPOX, CSF1PO, FES and vWA loci), and D1S80 locus. These markers were correctly detected from nails after 1 month, irrespective of environmental conditions. Thereafter, the detection rates were decreased to various degrees, except for nails left in air. The detection of longer DNA markers tended to be more difficult than the detection of shorter markers. Nails were more fragile in wet soil than in any other condition. However, nonspecific PCR products were not observed in any nail sample. Our results reconfirmed the usefulness of the nail as a specimen for forensic DNA analysis.     

Evaluating the prevalence of DNA mixtures found in fingernail samples from victims and suspects in homicide cases

An important aspect of homicide investigations is the identification of the persons that had the last contact with the victim prior to death. Violent crimes are frequently characterized by a struggle between the victim and the perpetrator where biological material can be expected to be exchanged between them.Forensic DNA typing enables the generation of genetic profiles by extraction and amplification of cellular material found under fingernails. The evidential value of these samples may be critical if the secondary contributor found in a DNA mixture, can be matched with a potential suspect, or through a DNA database search.The amount of biological material transferred under the fingernails during “casual” activities is not sufficient to genotype reportable mixtures. This may not be the case with homicide victims that may have struggled and died under violent circumstances.The aim of this study was to evaluate the prevalence of DNA mixtures found under the fingernails of both victims and suspected perpetrators of violent deaths.We present a retrospective study of 137 DNA profiles genotyped from fingernail samples of homicide victims and suspects, collected at the Israeli National Center of Forensic Medicine. The majority of the samples produced single source profiles (n = 107, 78%) that matched those of the donor's. DNA mixtures (n = 30, 22%) were found in increased frequency among victims (n = 25/100, 25%) compared to suspects (n = 5/37, 13.5%). Mixtures were sub-divided into high level (n = 15, 50%), low level (n = 9, 30%) and residual (n = 6, 20%), according to the number of the foreign contributors’ alleles. Thus, this distinctive group of homicide victims was found to express both elevated frequency of DNA mixtures together with highly informative value of the secondary foreign profiles, as compared to other studied populations. These findings support an important aspect for the criminal investigation in murder cases, where a struggle may have ensued and the identification of an additional profile found in a mixture from a fingernail sample may point to a possible perpetrator of the crime.     

Excoriations and contusions of the skin as artefacts in fictitious sexual offences

Some women reporting a sexual offence to the police inflict injuries on themselves, usually with the help of pointed and/or cutting tools, in order to make fictitious assaults more credible. If there is a classical pattern of the findings, such fictitious assaults are easier to identify. However, it is more difficult to distinguish genuine from fictitious injuries, if blunt force is used. This paper reports on 4 such cases, and the characteristics of self-inflicted excoriations and skin contusions are discussed. In the cases described, the excoriations were produced by scratching with the person's own fingernails or by rubbing the skin against a rough surface; contusion bleeding was caused by pinching (lifting and compressing skin folds with the fingers). The pattern of the injuries showed striking parallels to classical patterns: multiple lesions in grouped, parallel and symmetrical arrangement and of evenly minor intensity; preference of body regions within easy reach; no damage of the clothing, or if any, damage inconsistent with the injuries as described.     

A bone sample cleaning method using trypsin for the isolation of DNA

Cleaning the surface of bone samples is a necessary step to remove contaminants prior to isolating DNA for forensic DNA analysis. In this study, a simple trypsin method for cleaning bone samples prior to DNA isolation was developed. Cleaning the surface of human bone samples was achieved by the application of trypsin solution. Light microscopy and scanning electron microscopy results indicated that trypsin treatment was effective in removing the outer surface of bone samples. The yield of DNA isolated from trypsin-treated bone samples was sufficient for subsequent short tandem repeat (STR) analysis. STR analysis revealed no adverse effect on the DNA profile after the trypsin treatment. The data suggest that this trypsin method can potentially be an alternative cleaning method to mechanical cleaning methods.     

Age determination through DNA methylation patterns in fingernails and toenails

Over the past decade, age prediction based on DNA methylation has become a vastly investigated topic; many age prediction models have been developed based on different DNAm markers and using various tissues. However, the potential of using nails to this end has not yet been explored. Their inherent resistance to decay and ease of sampling would offer an advantage in cases where post-mortem degradation poses challenges concerning sample collection and DNA-extraction. In the current study, clippings from both fingernails and toenails were collected from 108 living test subjects (age range: 0–96 years). The methylation status of 15 CpGs located in 4 previously established age-related markers (ASPA, EDARADD, PDE4C, ELOVL2) was investigated through pyrosequencing of bisulphite converted DNA. Significant dissimilarities in methylation levels were observed between all four limbs, hence both limb-specific age prediction models and prediction models combining multiple sampling locations were developed. When applied to their respective test sets, these models yielded a mean absolute deviation between predicted and chronological age ranging from 5.48 to 9.36 years when using ordinary least squares regression. In addition, the assay was tested on methylation data derived from 5 nail samples collected from deceased individuals, demonstrating its feasibility for application in post-mortem cases. In conclusion, this study provides the first proof that chronological age can be assessed through DNA methylation patterns in nails.     

A mass spectrometry-based forensic toolbox for imaging and detecting biological fluid evidence in finger marks and fingernail scrapings

During a crime, biological material such as blood or vaginal fluid may become smeared on the fingers of the victim or suspect or trapped under their fingernails. The type of trapped fluid is extremely valuable forensic information. Furthermore, if either person touches an object at the crime scene with their ‘contaminated’ finger then a ‘contaminated’ finger mark may be deposited. Such marks have great value as they could identify not only who deposited the mark but also who they touched and which part of the body they touched. Here, we describe preliminary work towards a ‘toolbox’ of techniques based on mass spectrometry (MS) for the identification of biological fluid traces under fingernails or the imaging of them in finger marks. Liquid chromatography-multidimensional MS was effective for the detection of protein biomarkers characteristic of vaginal fluid and blood trapped under fingernails, even after hands had been washed. In regard to examination of finger marks for the presence of biological fluids, the most practical implementation of any technique is to integrate it with, but after, routine crime scene finger mark enhancement has been applied. Here, we demonstrate the usage of matrix-assisted laser desorption ionization-time of flight-MS for the detection and mapping of proteins and peptides from body fluids in finger marks, including marks enhanced using aluminium-containing magnetic powder and then ‘lifted’ with adhesive tape. Hitherto, only small molecules have been detected in enhanced, lifted marks. In a novel development, aluminium in the enhancement powder assisted ionization of small molecules in finger marks to the extent that conventional matrix was not required for MS.

     

CT and MR imaging features of pyogenic ventriculitis

BACKGROUND AND PURPOSE: Pyogenic ventriculitis is an uncommon manifestation of severe intracranial infection that might be clinically obscure. We hypothesized that determining characteristic imaging features of pyogenic ventriculitis in patients with appropriate risk factors might improve recognition of this severe infection. METHODS: Review of the medical records from 1990 to 2000 revealed 17 cases (12 men, five women) that satisfied inclusion criteria of abscess (n = 3) and/or positive cultures or increased white cells and protein in ventricular (n = 12) or cisternal (n = 1) cerebrospinal fluid. In one case, the diagnosis of ventriculitis was based on the combination of bacterial growth in lumbar cerebrospinal fluid and follow-up imaging. Staphylococcus species and Enterobacter species were the most common organisms. Two neuroradiologists independently evaluated imaging studies for hydrocephalus, ventricular debris, periventricular attenuation or signal abnormality, ependymal enhancement, and signs of meningitis or abscess. Sixteen studies in 11 patients were performed after the intravenous administration of contrast material. RESULTS: Ventricular debris was detected in 16 (94%) of 17 cases and was irregular in 13 (81%) of 16 cases. Hydrocephalus was present in 13 (76%) of 17 cases. Periventricular hyperintense signal was present in most (seven [78%] of nine) cases with MR imaging and was most conspicuous on fluid-attenuated inversion recovery sequences. Ependymal enhancement was detected in seven (64%) of 11 cases in which contrast material was administered. Signs of meningitis (eg, pial or duraarachnoid signal abnormality or enhancement) were present in 13 (76%) of 17 cases. Three cases had imaging signs of abscess. CONCLUSION: Ventricular debris was the most frequent sign of ventriculitis in this series. An irregular level was characteristic of debris in ventriculitis. Hydrocephalus and ependymal enhancement were less frequent signs. Detection of ventricular debris might facilitate diagnosis of pyogenic ventriculitis, a potentially fatal infection, and thus permit appropriate therapy.     

RNA/DNA co-analysis on aged bloodstains from adhesive tapes used for gunshot residue collection from hands

In cases of firearm related fatalities a systematic investigation at the scene of death is indispensable to differentiate between self-inflicted and homicidal gunshot injuries. A common method to preserve gunshot residues (GSR) is their collection using adhesive tapes. However, the biological material gathered at the same time by the tapes would be of special interest if backspatter, ejected from the entrance wound against the direction of fire, could be detected. In the present study we examined the success rate of co-analysis of RNA and DNA recovered from biological traces sampled with adhesive tapes. The material originated from eight cases of fatal gunshots, taken from the hands of suspects or victims, examined 5 to 19 years ago for GSR. For all types of adhesive tapes tested, quantity and quality of the co-extracted nucleic acids was insufficient for successful DNA profiling, but was sufficient for the detection of blood-specific micro RNA (miRNA). In summary, sampling trace evidence from the hands of persons involved in fatal gunshots with adhesive tapes has a long-term detrimental effect on biological traces.     

DNA analysis of fingernail debris using different multiplex systems: a case report

A 55-year-old male nurse was accused of having introduced his fingers by force into the anus of a 20-year-old female patient. Debris from the fingernails of the suspect recovered 2 days after the incident was analysed with the VNTR locus D1S80, the triplex PCR system AmpFlSTR Blue kit, the AmpFlSTR Profiler kit and the pentaplex system genRES MPX. The D1S80 singleplex reaction revealed indications of DNA from the victim in the fingernail debris of the left hand. Using the AmpFlSTR Blue kit and AmpFlSTR Profiler, DNA alleles of the victim were found at four additional loci, while allelic drop-out was observed at five other loci. Only the pentaplex kit genRES MPX revealed alleles at all loci which could be assigned to the victim. Calculation of likelihood ratios resulted in a value of 1.4 × 10⁵ using the combination of the multiplex systems AmpFlSTR Blue kit and AmpFlSTR Profiler and 2.8 × 10⁸ for the genRES MPX kit. This case demonstrates the high sensitivity of the new genRES MPX kit and that DNA profiling of fingernail debris is possible despite a time lapse of 2 days between the incident and recovery of the evidential material. Received: 30 March 2000 / Accepted: 19 September 2000     

交锁髓内钉联合负压封闭引流治疗胫骨干开放性骨折

目的探讨交锁髓内钉联合负压封闭引流（VSD）治疗胫骨干开放性骨折的疗效。方法我科自2008年1月～2011年3月运用磁力导航胫骨交锁髓内钉联合内置多侧孔硅胶管冲洗管负压封闭引流材料治疗GustiloⅡ型、Ⅲa型、Ⅲb型胫骨干开放性骨折33例,5～7d更换护创材料,创面肉芽新鲜后Ⅱ期缝合、游离植皮或组织瓣移植术修复皮肤缺损。结果 33例中29例Ⅰ期愈合1,例老年患者因合并糖尿病,血糖控制不佳发生迟发性骨髓炎2,例延迟愈合,1例骨不连。15例GustiloⅢb型皮肤缺损行皮瓣转移术修复,10例GustiloⅢa型行植皮治疗,8例GustiloⅡ型经换药后创面愈合。结论在彻底清创无高危因素的前提下,联合应用交锁髓内钉与负压封闭引流治疗GustiloⅢb以下型胫骨干开放性骨折是一种安全、有效的方法。     

The DNA‐Buster: The evaluation of an alternative DNA recovery approach

Touch DNA recovery techniques can have limitations, as their effectiveness depends on the substrate on which the DNA of a person of interest can be found. In this study, an in-house dry-vacuuming device, the DNA-Buster, was compared to traditional methods for its DNA recovery performance from items typically examined in forensic casework. The aim was to evaluate whether this dry-vacuuming approach can recover DNA efficiently, potentially complementing the well-established recovery strategies. For this, the performances of swabbing, taping, wet- (M-Vac®) and dry-vacuuming (DNA-Buster) were investigated quantitatively and qualitatively for touch DNA deposited on carpet, cotton sweater, stone, tile and wood. For the sweater, both vacuuming methods outperformed the other collection tools quantitatively. While the highest DNA amounts for the carpet were yielded by swabbing and taping, dry-vacuuming was equally good in reaching full DNA profiles, whereas less complete profiles were observed for the M-Vac®. For stone and tile, swabbing was optimal, whereas dry-vacuuming clearly underperformed for these substrates. Taping was the best recovery method for wood. Despite applying single donor DNA after thoroughly cleaning the items, undesired DNA mixtures were detected for all recovery techniques and all substrates. The overall research findings show first that the novel dry-vacuuming method is suited for DNA recovery from textiles. Secondly, they indicate that more attention should be paid to the substrate-collection dependency to ensure best practices in recovering genetic material in a precise, confident and targeted manner from the variety of forensic casework material.     

Developing a simple method to process bone samples prior to DNA isolation

Bone tissue is often used for recovering DNA samples for the purpose of human identification. However, the initial cleaning and sampling of the bone specimen is a labor-intensive and time-consuming step, which must be completed prior to isolating DNA. Thus, it is difficult to adapt the current method for automation. To address this issue, we have developed a simple processing method using a trypsin treatment prior to DNA isolation. The use of the trypsin-based procedure potentially reduces the amount of labor required by a physical method such as sanding. By incubating samples with the trypsin solution, the soft tissue and outer surface of the bone fragment samples are removed. The processed bone fragment or a portion of the fragment can then be used for DNA isolation.     

A molecular exploration of human DNA/RNA co-extracted from the palmar surface of the hands and fingers

“Touch DNA” refers to the DNA that is left behind when a person touches or comes into contact with an item. However, the source of touch DNA is still debated and the large variability in DNA yield from casework samples suggests that, besides skin, various body fluids can be transferred through contact. Another important issue concerning touch DNA is the possible occurrence of secondary transfer, but the data published in the literature in relation to the background levels of foreign DNA present on the hand surfaces of the general population are very limited.As the present study aimed at better understanding the nature and characteristics of touch DNA, samples were collected from the palmar surface of the hands and fingers (“PHF” samples) of 30 male and 30 female donors by tape-lifting/swabbing and subjected to DNA/RNA co-extraction. Multiplex mRNA profiling showed that cellular material different from skin could be observed in 15% of the PHF samples. The total amount of DNA recovered from these samples (median 5.1 ng) was significantly higher than that obtained from samples containing skin cells only (median 1.6 ng).The integrity of the DNA isolated from the donors’ hands and fingers as well as the prevalence of DNA mixtures were evaluated by STR typing and compared with reference STR profiles from buccal swabs. DNA integrity appeared significantly higher in the male rather than in the female subsample, as the average percentage of the donors’ alleles effectively detected in PHF profiles was 75.1% and 60.1%, respectively. The prevalence of mixtures with a foreign DNA contribution ≥20% was 19.2% (30.0% in the female PHF samples and 8.3% in the male PHF samples).The obtained results support the hypothesis that transfer of cellular material different from skin may underlie the occasional recovery of quality STR profiles from handled items. These results also suggest that gender may represent an important factor influencing the propensity of individuals to carry and transfer DNA through hand contact, possibly because of the differences in personal and hygiene habits between males and females.