Performance evaluation of the Scent Transfer Unit (STU-100) for organic compound collection and release.

The Scent Transfer Unit (STU-100) is a portable vacuum that uses airflow through a sterile gauze pad to capture a volatiles profile over evidentiary items for subsequent canine presentation to assist law enforcement personnel. This device was evaluated to determine its ability to trap and release organic compounds at ambient temperature under controlled laboratory conditions. Gas chromatography-mass spectrometry (GC-MS) analyses using a five-component volatiles mixture in methanol injected directly into a capture pad indicated that compound release could be detected initially and 3 days after the time of collection. Additionally, 15 compounds of a 39-component toxic organic gaseous mixture (10-1000 parts per billion by volume [p.p.b.(v)]) were trapped, released, and detected in the headspace of a volatiles capture pad after being exposed to this mixture using the STU-100 with analysis via GC-MS. Component release efficiencies at ambient temperature varied with the analyte; however, typical values of c. 10% were obtained. Desorption at elevated temperatures of reported human odor/scent chemicals and colognes trapped by the STU-100 pads was measured and indicated that the STU-100 has a significant trapping efficiency at ambient temperature. Multivariate statistical analysis of subsequent mass spectral patterns was also performed.

An investigation into the concurrent collection of human scent and epithelial skin cells using a non-contact sampling device.

In criminal investigations, the collection of human scent often employs a non-contact, dynamic airflow device, known as the Scent Transfer Unit 100 (STU-100), to transfer volatile organic compounds (VOCs) from an object/person onto a collection material that is subsequently presented to human scent discriminating canines. Human scent is theorized to be linked to epithelial skin cells that are shed at a relatively constant rate allowing both scent and cellular material to be deposited into the environment and/or onto objects. Simultaneous collection of cellular material, with adequate levels of nuclear deoxyribonucleic acid (nDNA), and human scent using a non-invasive methodology would facilitate criminal investigations. This study evaluated the STU-100 for the concurrent collection of human scent and epithelial skin cells from a porous (paper) and non-porous (stainless steel bar) object that was held for a specified period of time in the dominant hand of twenty subjects (10 females and 10 males). Human scent analysis was performed using headspace static solid-phase microextraction with gas chromatography-mass spectrometry (HS-SPME/GC-MS). A polycarbonate filter was used to trap epithelial skin cells which, upon extraction, were subsequently analyzed, inter-laboratory, using the quantitative polymerase chain reaction (qPCR). The STU-100 proved to be inadequate for collecting the minimum number of epithelial skin cells required to obtain nuclear DNA concentrations above the limit of detection for the qPCR kit. With regard to its use for human scent collection, a reduction in the number and mass of compounds was observed when compared to samples that were directly collected. However, when the indirect collection of human scent from the two different objects was compared, a greater number and mass of compounds was observed from the non-porous object than from the porous object. This outcome suggests that the matrix composition of the scent source could affect the efficacy of the human scent collected when using a non-contact, dynamic airflow sampling device. The findings from this study are of importance because although the STU-100 proved to not be suitable for collecting epithelial skin cells for DNA analysis, its non-contact capability allows for the possibility of other potential forensic evidence, like that of human scent, to be obtained.

Comprehensive characterization of commercially available canine training aids.

Effective and reliable training aids for victim recovery canine teams is essential for law enforcement and investigative purposes. Without adequate training aids, the rate of recovery for sub surface or surface human remains deposition using canine teams may be adversely affected and result in confusing information. The composition of three commercially available canine training aids that purportedly generate volatile components responsible for the odor of human decomposition is relatively simple and not closely related to those compounds experimentally determined to be present at the site of surface or sub-surface human remains. In this study, these different commercial formulations were chemically characterized using six different sampling approaches, including two applications of direct liquid injection, solid-phase microextraction (SPME), purge and trap, ambient preconcentration/thermal desorption, and cryogenic preconcentration/thermal desorption. Direct liquid injections resulted in the fewest number of detected compounds, while a cryogen based thermal desorption method detected the greatest number of compounds in each formulation. Based solely upon the direct liquid injection analysis, Pseudo™ Scent I was composed of approximately 29±4% and 71±5% of 2-pyrrolidinone and 4-aminobutanoic acid, respectively. This same analysis showed that Pseudo™ Scent II was composed of approximately 11±1, 11±1, 24±5, and 54±7% of putrescine, cadaverine, 2-pyrrolidinone, and 4-aminobutanoic acid, respectively. Headspace analysis was conducted to more closely simulate the process whereby a canine's nose would capture a volatiles profile. More compounds were detected using the headspace sampling method; however, the vast majority was not consistent with current data on human decomposition. Additionally, the three formulations were tested in outdoor and indoor scenarios by a double-blinded canine team, using a certified and specifically trained victim recovery canine with multiple confirmed recoveries, to determine if the formulations would be recognized by that canine as being related to human decomposition. The canine used in this study did not provide a positive response to any of the formulations tested in either test scenario. The implications for locating residual human decomposition odor in the absence of recoverable material are discussed in light of these data.

Characterization of the volatile organic compounds present in the headspace of decomposing human remains.

Law enforcement agencies frequently use canines trained to detect the odor of human decomposition to aid in determining the location of clandestine burials and human remains deposited or scattered on the surface. However, few studies attempt to identify the specific volatile organic compounds (VOCs) that elicit an appropriate response from victim recovery (VR) canines. Solid-phase microextraction (SPME) was combined with gas chromatography-mass spectrometry (GC-MS) to identify the VOCs released into the headspace associated with 14 separate tissue samples of human remains previously used for VR canine training. The headspace was found to contain various classes of VOCs, including acids, alcohols, aldehydes, halogens, aromatic hydrocarbons, ketones, and sulfides. Analysis of the data indicates that the VOCs associated with human decomposition share similarities across regions of the body and across types of tissue. However, sufficient differences exist to warrant VR canine testing to identify potential mimic odor chemical profiles that can be used as training aids. The resulting data will assist in the identification of the most suitable mixture and relative concentrations of VOCs to appropriately train VR canines.