What is gunshot residue

Composed of residues from the primer, projectile, and partially and unburned gunpowder, a chemical residue may be detectable and used to confirm a link to a person that may have been near to or fired a weapon, and even determine the proximity of a shooter to the target.

Bruker's compositional mapping solutions allow rapid elemental analysis and characterization of residues for most forensic investigation needs. The chemical pattern of gun shot residue around a point of impact or bullet hole reveals important details about the discharge of a weapon. A trained forensic scientist can use the patterns of firearm residues on a target compared to a test pattern series, i.

With 'on-the-fly' mapping the whole measurement area can be covered rapidly less than 1 hour where needed , while still retaining a high pixel resolution and high sensitivity for the elements typically found in gunshot residues.

This firearm residue pattern example shows the distribution of burnt and unburnt gunpowder characteristics that can be used for shooting distance determination. The quality of this rapid high-resolution scan is sufficient to identify locations of fragments of the projectile and even to see the structure of the canvas. Particles from the bullet, cartridge case and barrel are either indicative or commonly associated with, but on their own are not exclusive to, GSR. Forensic analysis involves the careful recovery of the microscopic metallic particles from clothing, surfaces or directly from the skin or hair of an individual.

The samples are coated with a thin layer of carbon and then examined for their characteristic elemental composition and morphology using a powerful scanning electron microscope SEM. GSR can provide supporting evidence for an investigation involving firearms and can help to determine:.

To browse these categories, please click on the links in the global navigation bar, and you will be presented with these links. If you have any questions, please see the Help Section or contact us. When a firearm is shot, in addition to the projectile s , a mass of debris comes out the muzzle. These gunshot residues GSR can include various primer residues, residues from projectiles, and partially burned and unburned gun powered particles.

The examination and analysis of GSR on items of evidence can allow determinations to be made as to weather a hole or defect is consistent with being caused by a bullet or other firearm-related projectiles. Once in the Laboratory, the Firearms Section can examine patterns of GSR on items of evidence to determine muzzle-to-target distance.

Additionally, GSR can be transferred to an individual by discharging a firearm, handling a firearm or fired ammunition components, or by contact with another object that has GSR on it.

The presence of GSR on a person may provide useful information linking an individual with an action that could transfer this residue to them. As a very general guide, after four to eight hours it is unlikely that residues will be found on a live and mobile individual's hands unless steps have been taken to preserve such evidence e. The method is applied to detect metallic and non-metallic species in a liquid sample even at a very low concentration. It works on the principle of optical emission spectrometry where plasma energy is given to the sample from the outer region leading to the excitation of atoms; when these atoms come at the lower position, spectrum rays are released, and their photon wavelength can be measured.

It is a bulk analysis technique for the analysis of elements present in the primer. The method allows very fast and multi-elemental analysis, but the limit is its sensitivity. It is more advantageous when an extracted sample was analyzed, in the GSR solution. The first scanning electron microscope with very high resolution came in by Manfred von Ardennes. In SEM, a beam of electrons is bombarded onto a specimen and then the image is formed von Ardennes, SEM is a powerful instrument equipped with an X-ray analyzer which emits X-ray providing a morphological feature of the element which needs to be analyzed.

The instrument is non-destructive and allows the highest specificity in detection of gunshot residue. The basic principle involved here is scattered electrons which are emitted from the surface of a specimen. The identification of elements based on morphological features is very important in detecting GSR particles.

The uses of morphological and elemental indicators help to differentiate one ammunition from another and to make a difference between firearms used to discharge a round, case, and bullet material was reported by Johnson et al. The residue collected from any region like hair, clothing, and hands showed positive results, thus decreased the danger of accidental sample contamination. In some cases, when inorganic GSR were not there, in that case, organic components are detected.

These organic components provide additional information about the sample and sometimes are helpful in making differentiation between the GSR and environmental residues. This study was performed by Collins et al. Collins et al. Hell miss et al. Detection of inorganic residues was largely practiced in the laboratory, but many scientists start to focus on detection of organic constituents of GSR, which originate from the propellant part of a firearm. The first combination of GC-MS came in and combining the computer-based mass spectrometer makes it more efficient in with the help of Robert E.

Finnigan Finnigan, The technique was applied to separate the mixture depending on the distribution between the stationary and the moving phases. Pyrolysis GC is an advanced form of gas chromatography where solid samples of forensic evidence are pyrolyzed at high temperatures to convert them into gaseous components.

Pyrolysis GC was performed by Newlon et al. Various detectors werecombined with GC to carry out the detection of organic residues like thermal energy analysis TEA , mass spectrometry MS , electron capture, and flame ionization. Andrasko et al. He combined GC with thermal energy analysis and mass spectrometry to get better results. According to Kirk bride et al.

Dalby et al. Joshi et al. Stevens et al. The advantage of using GC-MS without any sample preparation, pre-concentration, etc. Pigou et al. Gunshot residue analysis technique using solid-phase micro extraction. First given by Mikhail S.

Tswett when he did his study on separation of plant pigments. The liquid carries the sample pass through the column, different components retarded at different times. In HPLC, room temperature is sufficient to carry out the experiment.

Speers et al. Dahl et al. These stabilizers serve as an identification means of gunshot residue. Some scientists combine both high-performance liquid chromatography with pendant mercury drop electrode detector HPLC-PMDE and GC-TEA in combination to get better results, as these combinations lead to a strong or powerful result with more validity.

Wu et al. Solid-phase extraction SPE is a technique which is used to get the concentration and purify the sample. According to Cascio et al. Mathis et al. This method was found to be very useful in analysis of components in smokeless powder found in ammunition.

According to the non-target approach, the characterization of both unburnt smokeless powder and organic components was analyzed whether the firearm is of a different caliber, brand, age, etc.

Electrophoresis uses the same criteria of migrating on a stationary phase but differs as it does not use a moving liquid phase. In the capillary electrophoresis method, the analyst moved in the electrolyte solution under the influence of an electric field.

The system usually consists of vials, source, electrodes, and detector. Capillary electrophoresis along with mass spectrometry was first used by Richard D. Smith and his colleagues Krishnan, The technique of TLC uses the stationary phase as solid and liquid moving phases to separate the constituents of a mixture. Here, a thin layer of silica gel or aluminum oxide is prepared which serves as the stationary phase and the sample to be analyzed may be applied directly onto the plate.

The sample starts to rise based on capillary action. This way, the components of the sample are distributed between the stationary solid phase and liquid moving phase. Components with greater affinity to the moving phase travel faster than the components in the stationary phase. Retention value can be calculated using the formula:. Peak Peak, separated nitrocellulose from nitroglycerine which confirms the presence of flakes of smokeless powder using the TLC method. TLC with fluorescence was used by Meng et al.

First predicted by Adolf Smekal in and named after the Indian scientist C. The sample analyzed must be pure and colorless and the optical system made of glass or quartz. It consists of a source of light, sample illumination system, wavelength selector, and detector.

Doty et al. This method helps to identify and analyze various propellant components. Bueno et al. Results obtained gave specifications that the method is independent of Raman microscopes or collection software. The current need for detecting GSR requires high sensitivity and specificity to get reliable results. So, to go beyond these heavy instrumentation techniques to some shorthanded held device which gave result within a few minutes or hour.

For detecting the metallic constituents of gunshot residue, the anodic stripping voltammetry ASV method starts to implement. For organic constituents, cyclic voltammetry CV and square wave voltammetry are reported. From the acid wash, cotton swabbing and lifting using tape and adhesive can be overcome with the use of the abrasive method for gunshot residue particles.

In forensic laboratories, SEM and AAS are the first choice but these methods are time consuming and costly and require high-profile personnel. To overcome this, various electrochemical-based sensors are developed and given below in detail. The electrochemical method uses potential, current, and charge measurement to determine the analyte concentration. Also, the activity of analytes can be detected using the electrochemical method.

It is both a qualitative and quantitative technique based on electrochemical phenomena occurring within a medium. Even trace amounts of metal components can be analyzed. Various types of electrochemical techniques are there including ion-selective electrodes, coulometry, titrimetric method of analysis, and voltammetry method illustrated in Table 5. Analysis of GSR using the voltammetry method was very earlier practiced but got much attention over 35—40years as it is helpful in detecting the constituents very fast to other instrumental methods.

The technique was found to be reliable, sensitive, simple to perform, and effective and include portability too. The result obtained is accurate with less cost. The method cannot be applied to barium metal due to its high electrochemical potential. The most important elements found in gunshot residue containing inorganic components including lead, barium, antimony, and various other metals as shown in Table 1 used above need some advanced detection instead of color- and instrumentation-based techniques.

In electrochemical detection, the most important inorganic residue particles detected were Ba, Pb, and Sb. Many researchers worked on these metals, but antimony Sb was the least explored element electrochemically detected. Other worked on antimony metal based on the mercury electrode. They observe that the peak of antimony was overlapped by the copper strip peak. In , J. Heyrovsky Kovaleva et al. Along with several elements, only in one run lead and copper can also be detected with the help of various working electrodes.

Here, samples were shifted to Nalgene bottles these bottles prevent contamination , and then, voltammogram was ran using a polarography analyzer in nitric acid and hydrochloric acid. The time of deposition observed was 80— s. Detection time was around 2 h for lead Pb and antimony Sb determination. In , Dewald et al.

Samples were extracted using cotton-based Q-tips dissolved in acid for 12—16 h and a voltammogram was run in a KNO 3 hydrazine sulfate solution for s. A single scan detects lead and antimony on an electrode surface. Liu et al. Samples were collected using acid wash for 10 min with a detection limit of 1.

It is easy to make, install, and operate which works reliably without adjustment or maintenance. Diagram metric demonstration of electrochemical cell for gunshot residue particle analysis using ASV.

The data was compared with AAS data which uses square wave voltammetry. Rodriguez et al. Here, Bi was collected on a carbon paste electrode with a deposition time of 60 s.

LOD of Pb was detected to be 0. Mahoney et al. These strips were used to detect Pb and Cu which gave results as no contact with GSR, secondary contact, and subsequent firearm discharge. From this method, important inorganic components were analyzed like lead and antimony, but barium was not detected because of negative stripping potential as reported earlier.

The Arrow Figure shows the Abrasive Stripping Voltammetry simplified method where firearm shoot, and Gunshot Particles were Swiped, Scanned and then studied whether firearm discharged or not.

There is a huge demand to analyze the organic constituents present in gunshot residue based on electrochemicals. Since various occupational and environmental contaminants inhibit the instrumental and color analyses, electrochemical detection in gunshot residue needs to be performed. Several researches were carried out in seawater to analyze nitro explosive compounds which consist of several organic species as reported in literature. Thus, organic metals important forensically need to be analyzed and it is outlined here in detail with all known developed protocols for electro analysis detection.

So the supplementary norm for analyzing the GSR requisite needs to be taken. This proves to be helpful in detecting gunshot residues. Further, in , Wang et al. This work helps forensic scientists to get reliable work based on CV. The system generated was even not applicable to real samples but was the first example of a hand-held instrument for both constituents of GSR.

The amperometry method work on the principle of production of a current when potential is applied between the two electrodes. The basic electrode used in the amperometry sensor is the Clark oxygen electrode which consists of a platinum cathode where oxygen is reduced and silver chloride AgCl acts as a reference electrode.

In these sensors, current response is used to detect the concentration of analyte Jian et al. Nitrite is an inorganic component of gunshot residue generated from primer constituents. Nitrite presence in gunshot was detected using various color tests and instrumental techniques but gave no quantitative determination. So, to overcome this problem, an amperometry sensor was developed to determine nitrite in gunshot residue.

The method employed is simple, effective, rapid, and easy to perform. Some cases of firearms include several suspects, so in these cases, fast testing of GSR is applied. In this test, flow injection analysis combined with the electrochemical method was used to detect with less contamination of the sample, great precision value, and better accuracy and less amount of reagent required. The surface area was enhanced by using platinum, palladium, gold, and silver on nano and micro scales.

For the detection of nitrite, palladium particles were found to be very suitable as they have good conductive and catalytic nature. The activity of Pd can be enhanced further when they are subjected to carbon material-based nanoparticles Promsuwan et al.

The amperometry sensor firstly includes preparation of the Pd-GCMS composite as described by Sirisaeng and his colleagues with some modification Sirisaeng et al.