The significance in detecting and determining out-of-scope findings for volatile organic compounds in forensic casework

Abstract

To provide an appreciation for identifying unknown peaks in headspace gas chromatography and a process for reporting additional information for volatile organic compounds (VOCs) in cases. VOCs are frequently abused as inhalants (gases or solvents). They are often abused due to their accessibility and low cost. VOCs are used in a variety of products including household and commercial items such as gasoline, compressed air duster products, nail polish, glues, paints, and varnishes. They are abused because they can be inhaled or insufflated. Abusing these substances can lead to serious health problems including the possibility of death due to chemical asphyxia and/or central nervous system depression. Routine testing procedures can be used to identify many such compounds. Cases for which VOCs were detected that were not in the routine scope of testing were identified during 2020 to 2022. The samples (all blood except for one gastric case) were originally analyzed using either headspace gas chromatography with flame ionized detection (GC/FID) and/or headspace gas chromatography/mass spectrometry (GC/MS). Where possible, if laboratory testing was performed in addition to volatile testing, volatile testing was performed first to limit evaporation of volatile compounds. Based on the results the sample either had further testing performed or an experienced forensic toxicologist was consulted to determine the next course of action. Unknown peaks identified through volatile toxicological testing include 1,1-Difluoroethane (DFE), Chlorodifluoromethane (Freon22), and components found in gasoline such as butane, pentane, benzene, etc. It is important to establish a process to determine when additional peak identification is needed. Frequently, this is provided through case history, but that is not always readily available. Depending on the sample matrix, the detected analytes, and their volatility, results were reported either qualitatively or quantitatively. Case reports for select samples will be discussed further to demonstrate the inherent value of this approach. Challenges exist with the use of headspace gas chromatography in the identification of unknown peaks. These peaks can provide vital information about a case. It is important to be vigilant when assessing such data since these peaks can often be missed or overlooked due to limits in the method. Identified unusual peaks in the chromatography should be interpreted with caution and additional case information needs to be sought. The significant findings from the out-of-scope headspace gas chromatography analysis can provide key toxicological information in cases when no other additional results are found.