Aim: To determine the level of contamination of police vehicles in the Zagreb Country Police Administration, which are used for suspects and other event participants transportation with GSR particles, and to examine the relationship of selected variables with vehicle contamination. Methods: From December 8, 2021, to April 13, 2022, 65 police vehicles were sampled in 17 police stations. A total of 195 samples were collected from the driver's seat, back seat, and backrest using GSR stubs. Examination of the extracted samples was carried out using a scanning electron microscope. Any vehicle on which at least one GSR particle was found in at least one sample was considered a positively contaminated vehicle, whereby characteristic and indicative particles were considered separately. The proportion of contaminated vehicles and the number of particles were calculated depending on the location and type of particles. A logistic regression model was used to examine the possible influence of variables collected by the questionnaire on vehicle contamination as an outcome. Results: Characteristic GSR particles were found in 41 vehicles (63.1%), while indicative particles were found in 46 vehicles (70.77%). Characteristic particles were present in 33.8% of samples taken from the driver's seat and in 24.6% of samples taken from the back seat or the backrest of the back seat. Indicative particles were present on the driver's seat in 33.8% of samples, on the back seat in 30.77%, and on the back backrest in 35.38% of samples. No statistically significant difference was observed between the proportion of positive samples taken from the driver's and back seat or samples taken from the driver's seat and backrest of the back seat, as well as no difference in the proportion of vehicles contaminated with characteristic and indicative particles (P > 0.05). A total of 228 characteristic GSR particles and 166 indicative GSR particles were found, with the most frequent number of confirmed particles in the sample being 1. No statistically significant correlation was observed between the number of characteristic and indicative particles (𝜏 = 0.148, P = 0.346). Logistic regression analysis showed that, among the considered variables, vehicle contamination could only be affected by the transportation of persons who participated in an event where firearms were used (P = 0.030). Conclusions: The presence of characteristic GSR particles was confirmed in almost 2/3 of the vehicles, which may point to risk from secondary contamination of persons transported in vehicles, but considering the small number of identified particles, this risk is not high. It can be expected that the share of contaminated vehicles by the sampled areas considered will be equal, as well as the share of vehicles contaminated with characteristic and indicative particles. However, contamination containing indicative particles does not indicate contamination containing characteristic GSR particles. Transportation of persons who participated in an event where firearms were used can be a potential contamination risk factor, pointing to additional caution in these cases.