New incompatibilities uncovered using the Promega DNA IQ™ chemistry

Comparison of three DNA extraction methods tested on illicit drug-related powders

The detection of human DNA on and within illicit drug preparations is novel and a focus of current research. Previous studies have indicated that certain drug-related powders present in illicit drug preparations can interfere with downstream DNA analysis when directly added to the PCR. Therefore, it is important to determine if these drug-related powders are effectively removed during the DNA extraction or whether traces of powder remain to interfere with DNA processing. Three extraction methods were selected to assess their efficiency at removing drug-related powders for downstream processes using DNA from both saliva and touch depositions. This is the first study to compare efficiencies of DNA extraction methods from drug-related powders. The extraction methods compared were the DNA IQ™ System, the QIAamp® DNA Investigator Kit and the combination of a simple lysis step followed by use of the Microcon® DNA Fast Flow device. Saliva was added to dimethylsulfone (DMS), nitrostyrene and PROSOLV® tablet mixture to determine the effect of powder type (based on solubility). Saliva was also added to 0, 50, 200 and 400 mg of DMS to determine the effect of an increase in DMS quantity. Trace DNA was deposited onto DMS using a worn glove approach. These samples were re-tested six months post-DNA deposition and profiled for further comparisons. Ten replicates were conducted for each condition with five replicates of saliva positive controls per method (n = 255 samples). A subset of samples was chemically analysed to determine if DMS was present in the final DNA eluant. The readily soluble DMS did not interfere with any of the extraction methods at lower amounts, however increasing the DMS to 400 mg reduced the relative DNA yields using the Microcon® and Investigator methods. The tablet mixture reduced the relative DNA yield of all three methods, however the nitrostyrene (which was relatively insoluble) only reduced the relative DNA yield of the DNA IQ™. The Investigator method performed the best with the trace samples, followed by the Microcon® method and then the DNA IQ™. DMS was detected in all extracts chemically analysed from the DNA IQ™ and Microcon®, whereas only one sample tested from the Investigator kit contained DMS in the extract and was in a relatively low amount compared to the other samples. Not one kit outperformed the others in all comparisons, however the Investigator kit was the most efficient overall at optimising the DNA yield whilst also removing the powders more effectively.

Persistence of touch DNA on commonly encountered substrates in different storage conditions

The persistence of touch DNA deposited after realistic handling of items typically encountered in forensic investigations has been the subject of few studies. Understanding the long-term persistence of touch DNA on different substrates in varying conditions can be central to the effective triage of samples for further processing. As the time between an alleged incident and collection of evidence may vary from a few days to years after an alleged event, this study assessed three different common substrates for the persistence of touch DNA over a time span up to 9 months. These substrates included fabric, steel, and rubber, each of which were handled in a way to imitate what may happen during a criminal act. The three substrates were exposed to two different environments for up to 9 months: inside a dark cupboard with no traffic to act as a control and an outside semi-exposed environment. Ten replicates from each of the 3 substrates were tested at 5 time points to create 300 samples. All samples were processed using a standard operating workflow to provide genotype data after exposure to different environments. It was found that the fabric samples produced informative STR profiles (defined here as 12 or more alleles) up to the 9 month timepoint for either environment. The rubber and steel substrates for the inside condition produced informative STR profiles up to the 9 month timepoint, but only generated informative STR profiles for the outside condition up to 3 and 6 months, respectively. These data add to our understanding of the external factors that affect DNA persistence.

Recent Advances in Enhancement Techniques for Blood Fingerprints

The blood fingerprint enhancement is not so eye-catching as latent fingerprint development in forensic community, but it is indeed an important piece of evidence for personal identification, forensic analysis and even reconstruction of crime scenes. In over past ten years, novel reagents, advanced materials and emerging techniques have growingly participated in blood fingerprint enhancement, which not only leads to a higher level of developing sensitivity, selectivity and contrast, but also endows blood impressions with more forensic significance. This review summarizes recent advances in conventional chemical reagents targeting at heme, protein and amino acid as well as emerging enhancement techniques based on advanced materials, new equipment or methods. Some critical issues in forensic science are also discussed, including partial blood fingerprint enhancement, false positive of developing reagents, the compatibility of blood enhancement technique and DNA, fingerprint age determination, and so on. Finally, we have proposed several urgent problems to be solved and the prospects of some promising techniques were proposed in the field of blood fingerprint enhancement in future work.

The effect of DNA recovery on the subsequent quality of latent fingermarks: A pseudo-operational trial

The recovery of fingermarks and DNA from the same location at a crime scene can be problematic because of contamination issues associated with powdering or laboratory-based visualisation processes and/or the perceived destructive impact of commonly employed 'swabbing' approaches to DNA recovery. Previous research in a controlled environment demonstrated that it was possible to recover DNA and latent fingermarks from the same location on various substrates when an adhesive approach to DNA recovery was used. The aim of this research was to conduct a pseudo-operational trial into the dual recovery of DNA and fingermarks using gel lifters for DNA recovery. Participants were asked to voluntarily and anonymously donate a wide variety of porous and non-porous substrates post handling. No instruction as to fingermark deposition nor environmental storage was provided. BVDA gel lifters were applied to the substrates to replicate DNA recovery followed by the application of fingermark visualisation processes. The number and quality of the fingermarks was established using a grading approach. Application factors were also investigated to consider the effects of user variation. The results demonstrated that it was possible to recover DNA and fingermarks considered to be capable of supporting an identification. Fingermark quality post lifting was dependant on the substrates used. The weight applied to the gel during its application was a lesser contributing factor than the duration of its contact with the surface. There was a greater chance of leaving the fingermarks unaltered with the application of a low weight and instantaneous retraction.

Evaluation of DNA Extraction Methods for Processing Fingerprint Powder-Coated Forensic Evidence

In unison, fingerprinting and DNA analysis have played a pivotal role in forensic investigations. Fingerprint powders that are available on the market can come in a range of colors and with specific properties. This study evaluated the efficiency of DNA extraction from samples coated with 3 brands of fingerprint powders: Lightning, Sirchie, and SupraNano, covering a range of colors and properties. A total of 23 fingerprint powders were tested using the Chelex, Promega DNA IQ™, and Applied Biosystems™ PrepFiler™ DNA extraction protocols. The DNA IQ™ and PrepFiler™ methods extracted higher yields of DNA in comparison to Chelex, which also accounted for better quality of PowerPlex x00AE; 21 DNA profiles recovered. There were no signs of degradation or inhibition in the quantification data, indicating that samples returning low DNA yield was due to interference during DNA extraction and not PCR inhibition. DNA profiles were recovered from the majority of fingerprint powders with only a single powder, Sirchie Magnetic Silver, failing to produce a profile using any of the methods tested. A link was observed between the DNA extraction chemistry, fingerprint powder property, that is, nonmagnetic, magnetic and aqueous, and the brand of fingerprint powder. Overall, the DNA IQ™ method was favorable for nonmagnetic fingerprint powders, while magnetic fingerprint powders produced more DNA profiles when extracted with the PrepFiler™ chemistry. This study highlights the importance of screening DNA extraction chemistries for the type of fingerprint powder used, as there is not a single DNA extraction method that suits all fingerprint powder brands and properties.

Compatibility of DNA IQ™, QIAamp® DNA Investigator, and QIAsymphony® DNA Investigator® with various fingerprint treatments

Latent fingerprint and touch DNA are the two most important contact evidence for individualization in forensic science which provide complementary information that can lead to direct and unequivocal identification of the culprit. In order to retrieve useful information from both fingerprints and DNA, which are usually mingled together, one strategy is to perform fingerprint examination prior to DNA analysis since common DNA sampling technique such as swabbing could disturb or even destroy fingerprint details. Here, we describe the compatibility of three automatic DNA extraction systems, namely, DNA IQ™, QIAamp^® DNA Investigator, and QIAsymphony^® DNA Investigator^®, with respective to the effects of various fingerprint detection techniques. Our results demonstrate that Super Glue fingerprint treatment followed by DNA IQ™ extraction shows better effectiveness in DNA profiling. Aluminum powder dusting offers the least interference to the three DNA extraction systems above. Magnetic powder dusting, on the other hand, strongly impedes DNA recovery. Physical Developer is the most intrusive, which yields profiles with poor quality, including lower peak heights, poor peak height ratios, and poor intra-color balance. In terms of the choice of extraction method, DNA IQ™ system is recommended for sampling after fingerprint treatments, but not the two DNA Investigator systems.