Forensic recovery of identification from shell casings
Inventors
Hewitt, F. Curtis • Sugrue, Tierney • Ludolph, Benjamin • Schulte, Kathleen
Assignees
Publication Number
US-11920127-B2
Publication Date
2024-03-05
Expiration Date
2040-12-04
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Abstract
Non-destructive methods and devices are disclosed herein for overcoming the limitations associated with analyzing shell casings and other cylindrical items for biomolecular and fingerprint extraction and analysis. In a preferred embodiment of these methodologies and devices, the open end of a spent shell casing (or like object) is plugged with a handle. This approach reduces the risk of sample contamination by gunpowder residue, while also providing a convenient means for handling the shell casing that reduces the risk of contamination or sample loss. Spin baskets (or extraction tubes) are provided which may be customized to different shell casing diameters, thereby substantially reducing the volume of extraction buffer required for sample collection and enable ease of centrifugation. A strong surfactant is preferably utilized during collection, which may reduce the amount of time needed for collection to just minutes. The surfactant is preferably of a type that draws on the extracellular nature of DNA in the sample in such a way as to almost instantaneously pull it into solution upon exposure to the buffer. The full buffer volume is then rapidly collected through the spin basket for DNA purification. Additionally, the use of magnetic beads to rapidly separate DNA from metal ions and other inhibitory agents is a primary advancement of the methods. The systems and methodologies disclosed herein offer a possible paradigm shift for forensic laboratories as they analyze challenging types of casework evidence. In particular, these systems and methodologies may be utilized to improve the preservation, recovery and analysis of DNA, proteins, other forensically-relevant biomolecules, chemical, radiological, nuclear, or explosive residues, and fingerprints collected from shell casings or other like samples.
Core Innovation
The invention discloses non-destructive methods and devices designed to improve forensic analysis and biomolecular extraction from shell casings and other cylindrical evidentiary samples. A key aspect is plugging the open end of a spent shell casing with a handle-attached plug, which prevents contamination from gunpowder residue inside the casing and provides a convenient means for handling the casing, reducing the risk of sample loss or contamination. Spin baskets customized for different shell casing diameters are used to minimize the volume of extraction buffer required and facilitate centrifugation for rapid separation.
The methods employ a strong surfactant-based collection buffer that rapidly solubilizes extracellular DNA in minutes by instantly pulling it into solution upon exposure. After exposure, the buffer containing solubilized biomolecules is separated from the casing via centrifugation using the spin basket. Additionally, magnetic beads are utilized to rapidly separate DNA from metal ions and other inhibitors that degrade DNA. These features collectively maximize recovery and analysis efficiency of DNA, proteins, and other biomolecules from challenging sample types like shell casings.
This approach addresses the problems inherent in conventional methods of DNA collection from shell casings, namely: low DNA yield due to small surface area; mixture of materials from multiple handlers; DNA degradation due to heat and metal ions such as copper; contamination from gunpowder residue; and difficulties balancing swabbing versus submersion techniques that risk oxidative damage and inhibitors. By using sealing plugs, customized spin baskets to reduce buffer volume, and surfactants that rapidly solubilize DNA, the methods overcome these limitations to provide a more effective forensic sample recovery and analysis process.
Claims Coverage
The patent includes one independent method claim with multiple inventive features covering the apparatus and method for forensic processing of shell casings.
Method of plugging shell casing to prevent contamination
The method comprises disposing a plug into the shell casing's open first end to form a plugged shell casing, with the plug pressingly engaging the interior surface to seal the opening. The plug may have a peripheral groove with an O-ring to improve sealing.
Use of a handle attached to the plug for convenient handling
A handle is attached to the plug, extending outside the shell casing to provide a convenient means for manipulating and handling the casing, minimizing contamination risk during processing.
Insertion of the plugged shell casing into a container with liquid medium to solubilize forensic samples
The plugged shell casing is inserted into a container, such as a spin basket, containing a liquid medium (e.g., a collection buffer with a chelator) that solubilizes at least part of the forensic sample deposited on the casing.
Separation of solubilized sample from the shell casing by centrifugation
Following solubilization, the liquid medium containing the extracted biomolecules is separated from the casing by centrifugation, facilitating efficient recovery of the forensic sample.
Use of magnetic beads to isolate proteins and DNA from inhibitors
The solubilized sample can be mixed with beads that bind proteins, allowing isolation of these loaded beads and subsequent stripping to obtain protein solutions for forensic analysis, thereby separating DNA and proteins from metal ions and other inhibitory substances.
Alternative methods for disposing plugs using curable liquid or molten materials
Disposing the plug may include placing a curable liquid or molten material into the casing opening, curing or solidifying it, with optional insertion of a handle into the material before solidification.
The claims collectively cover a forensic method and device involving sealing a shell casing with a plug and handle, submerging it in a collection buffer within a spin basket for solubilizing forensic samples, rapid centrifugation-based separation of the liquid sample, and use of magnetic beads for enhanced biomolecular isolation, while variants include plug formation by curing or solidification of materials.
Stated Advantages
The plug prevents the collection buffer from contacting gunpowder residue inside the shell casing, preventing co-extraction of compounds that may degrade DNA or inhibit analysis.
The handle attached to the plug simplifies handling of shell casings, reducing risk of contamination or sample loss.
Custom-sized extraction tubes or spin baskets minimize the volume of collection buffer required, reducing dilution effects and increasing recovery of biomolecules.
The use of a strong surfactant rapidly solubilizes biomolecules, greatly reducing the time that DNA and DNA-degrading metal ions coexist in solution.
Centrifugation through custom spin baskets enables quick separation of collection buffer from the shell casing.
Magnetic beads allow rapid separation of DNA from metal ions and other inhibitory agents, improving sample purity.
These improvements collectively reduce reagent volumes, shorten analysis time, lower skill-level requirements, and offer notable advancements over existing forensic protocols for shell casing evidence.
Documented Applications
Forensic analysis of DNA, proteins, and other biomolecules recovered from bullet shell casings.
Non-destructive extraction and analysis of fingerprints from shell casings.
Analysis of chemical, radiological, nuclear, or explosive residues collected from shell casings or similar evidentiary samples.
Use in forensic laboratories to process challenging casework samples involving shell casings.
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