## 3 Results
### Analytical Characteristics of the Optimized SEM-EDS Method
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & & & & & **Number of Particles Characteristic of GSR** & & & \\ \hline Person’s number & P1 & P2 & P3 & P4 & P5 & P6 & P7 & P8 & P9 \\ \hline Time after shooting, h & 0 & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 \\ \hline  & & & & & & & & \\  & & & & & & & & \\ \hline winter 2021 & 19 & 13 & 9 & 3 & 1 & 0 & 0 & 0 & 0 \\ \hline summer 2021 & 14 & 12 & 6 & 2 & 0 & 0 & 0 & 0 & 0 \\ \hline  & & & & & & & & & \\ \hline winter 2021 & 12 & 10 & 8 & 1 & 2 & 0 & 0 & 0 & 0 \\ \hline summer 2021 & 8 & 4 & 2 & 0 & 1 & 0 & 0 & 0 & 0 \\ \hline  & & & & & & & & & \\ \hline winter 2021 & 14 & 8 & 6 & 3 & 2 & 0 & 0 & 0 & 0 \\ \hline summer 2021 & 11 & 4 & 3 & 5 & 1 & 0 & 0 & 0 & 0 \\ \hline mean & 13 & 9 & 6 & 2 & 1 & 0 & 0 & 0 & 0 \\ \hline SD & 4 & 4 & 3 & 2 & 1 & 0 & 0 & 0 & 0 \\ \hline \end{tabular}
\end{table} 
Table 6: Number of particles characteristic of GSR as a function of time after shooting with a low-caliber ammunition. Each person made one shot. Figure 3: Number of particles characteristic of GSR as a function of time after shooting with high-caliber ammunition: Zastava M70 AB2 rifle (7.62 \(\times\) 39 mm) (blue line), Zastava M48 bolt-action rifle (7.92 \(\times\) 57 mm) (orange line), and RPD light machine gun (7.62 \(\times\) 54 mm) (grey line). The experiments were carried out during: **(A)** the winter season and **(B)** the summer season. Table 5 and Figure 4 show the results from the study of GSR particles obtained by three types of low-caliber ammunition. The number of detected particles characteristic of GSR were 75% below the number of particles generated by high-caliber ammunition. The GSR particles could be found on the hand of a shooter who performed normal daily activities for up to 4 h after shooting, regardless of the season and the type of gun. In both series of experiments with high- and low-caliber ammunition, the slope of the curves in the first 3 h was high, demonstrating that the main loss of particles occurred during the first 3 h after the shooting. A decay in the particle loss was observed between 3 and 6 h, depending on the calibers and types of firearms used in this experiment. Five hours after the firearm discharge, particles characteristic of GSR were found in one of six series of experiments. Therefore, five hours could be proposed as a threshold for the time interval if only one shot is to be assumed. The mean number of characteristic GSR particles calculated from six series of experiments as a function of the time interval between shooting and sampling is presented in Figure 5. An average of two calibers of firearms was calculated, with three firearms in each group. All experiments were repeated during two seasons: summer and winter. Based on the mean results, it was found that the polynomial model can predict the GSR fate with \(\mathbb{R}^{2}>0.99\). The equations are presented in the Figure 5 inset. Figure 4: Number of particles characteristic of GSR as a function of time after shooting with low-caliber ammunition: Walther PPK pistol (7.65 \(\times\) 19 mm) (blue line), Glock 19 pistol (9 \(\times\) 19 mm) (red and orange line), and Zastava M70 pistol (7.65 \(\times\) 17 mm) (green and grey line). The experiments were carried out during: (**A**) the winter season and (**B**) the summer season. Evaluation of the Number of Characteristic GSR Particles as a Function of the Number of Shots and Sampling Time  
To verify the previous hypothesis, the time dependence of the number of persistent GSR particles on the shooter's right hand (the hand used for shooting) with the number of shots was investigated. Nine participants in the test fired from 1 to 9 shots, and the sampling of GSR was carried out at 0 to 8 h after the discharge. The results are presented in Table 7 and Figure 6.