Building a ground-truth fingerprint dataset for proficiency testing and research.

This article outlines the process used to collect fingermarks in a controlled environment, encode, and store the fingermark images. It was important that the fingermarks resemble the type of evidence that would be found at a crime scene. This meant using a variety of substrates, development techniques, and residues. The dataset also includes non-mates; the manner in which close non-matches were found using an Automated Fingerprint Identification System (AFIS) will be discussed. An efficient workflow was created which allowed the RCMP to capture 3011 fingermark images from 62 individuals. This is the foundation of the dataset that will be used for future research and proficiency testing by the RCMP. Two vital lessons learned during the process were, the importance of thoroughly cleaning objects before use and to ensure proper quality control checks were in place, including verification through a fingerprint comparison. Since the data is being used in proficiency testing, it is currently unavailable for public use.

New incompatibilities uncovered using the Promega DNA IQ™ chemistry.

Over the years, the Promega DNA IQ™ System was proven an effective technology for the production of clean DNA from a wide variety of casework specimens. The capture of DNA using the DNA IQ™ paramagnetic beads, however, was shown to be affected by a few specific chemicals that could be present on exhibits submitted to the laboratory. In this study, various blood and latent fingerprint enhancement reagents/methods, marker pens and adhesive tapes, applied at the crime scene or in the forensic laboratory on casework exhibits or used to collect biological material, were tested for their compatibility with the DNA IQ™ technology. Although no impact on DNA recovery was observed for most reagents, the MAGNA™ Jet Black fingerprint powder and three 3M Scotch(®) adhesive tapes were shown to severely or completely inhibit DNA binding onto the DNA IQ™ beads. The effect of MAGNA™ Jet Black on DNA recovery could be counteracted by separating the magnetic powder from the lysates by centrifugation or filtration, prior to DNA extraction. High quality STR profiles were obtained from samples subjected to MAGNA™ Jet Black suggesting it does not impact DNA integrity.

Elimination of bioweapons agents from forensic samples during extraction of human DNA.

Collection of DNA for genetic profiling is a powerful means for the identification of individuals responsible for crimes and terrorist acts. Biologic hazards, such as bacteria, endospores, toxins, and viruses, could contaminate sites of terrorist activities and thus could be present in samples collected for profiling. The fate of these hazards during DNA isolation has not been thoroughly examined. Our goals were to determine whether the DNA extraction process used by the Royal Canadian Mounted Police eliminates or neutralizes these agents and if not, to establish methods that render samples safe without compromising the human DNA. Our results show that bacteria, viruses, and toxins were reduced to undetectable levels during DNA extraction, but endospores remained viable. Filtration of samples after DNA isolation eliminated viable spores from the samples but left DNA intact. We also demonstrated that contamination of samples with some bacteria, endospores, and toxins for longer than 1 h compromised the ability to complete genetic profiling.

The fate of the chemical warfare agent during DNA extraction.

Forensic laboratories do not have the infrastructure to process or store contaminated DNA samples that have been recovered from a crime scene contaminated with chemical or biological warfare agents. Previous research has shown that DNA profiles can be recovered from blood exposed to several chemical warfare agents after the agent has been removed. The fate of four toxic agents, sulfur mustard, sodium 2-fluoroacetate, sarin, and diazinon, in a lysis buffer used in Promega DNA IQ extraction protocol was studied to determine if extraction would render the samples safe. Two independent analytical methods were used per agent, selected from GC-MS, 1H NMR, 19F NMR, (31)P NMR, or LC-ES MS. The methods were validated before use. Determinations were carried out in a semi-quantitative way, by direct comparison to standards. Agent levels in the elution buffer were found to be below the detectable limits for mustard, sarin, sodium 2-fluoroacetate or low (<0.02 mg/mL) for diazinon. Therefore, once extracted these DNA samples could be safely processed in a forensic laboratory.