The differential diagnosis between injury patterns resulting from falls from heights and car-pedestrian collisions is crucial, especially in cases where the death was unwitnessed, and the body was not discovered immediately. This scenario is more common in urban environments with a high density of elevated structures, such as buildings, pedestrian overpasses, and bridges.

Our research identified several injury patterns that are significantly associated with either pedestrian or fall victims, as detailed in Tables 1, 2, 3 and 4.

The comprehensive review of forensic reports for 232 cases revealed that, in the analysis of internal organ injuries, statistically significant differences were observed only in the frequency of bilateral lung injuries and liver (p < 0.001). In our study, brain injuries were sustained by approximately 35% of both pedestrians (36 out of 103) and individuals who fell from heights (45 out of 129). Other studies reported that brain injuries are more common in pedestrian impacts, with prevalence rates reaching up to 94.4% when brainstem injuries are included [15,16,17]. We found also that bilateral lung injuries were significantly more common in falls from height (33.3%) than in pedestrians (13.6%). However, there is considerable variability in the frequency of lung involvement reported in scientific Literature of both these fatalities [13, 18,19,20].

In our study, the prevalence rates for unilateral kidney injuries were 9.7% in pedestrians and 10.9% in falls from heights, with no statistically significant difference between the two groups. Moreover, bilateral kidney involvement was observed in 1.9% of pedestrians and 1.6% of fall victims and was not a reliable indicator for determining the cause of death. Bansal et al. [18], reported no renal injuries among 40 fatal falls from height, suggesting the organs’ protection due to their location and size.

We also found that liver injuries were significantly more frequent in falls from height (49.6%) compared to pedestrians (28.2%). From a practical perspective and based on direct experience, it is well-established that falls from heights pose a significant risk of injury due to deceleration forces, which usually are considerably greater than those encountered in pedestrian impacts. However, these observations are variable, as they depend on factors such as the speed of vehicles and the height of the fall. Consequently, a higher frequency of organ injuries can be anticipated in falls from heights, especially affecting anatomical structures involved in organ fixation, such as the hilar regions. These injuries often present as characteristic tearing wounds in the perihilar area, involving major vessels and surrounding structures. Therefore, the higher prevalence of bilateral lung injuries and liver injuries observed in our study of falls from heights is consistent with these expectations.

Analysis of injury laterality is also crucial. Generally, pedestrians tend to experience lateral trauma upon initial impact. In contrast, falls from height are more likely to result in impacts on the frontal plane, with the head being the most common site of first impact. This difference in impact dynamics may explain the statistical variation observed in the analysis of bilateral lung injuries [21,22,23].

Concerning liver involvement, the observations from our case analysis align with expectations based on the aforementioned discussion. Direct impacts typically result in lacerations of the hepatic parenchyma, which are more common in pedestrians hit by cars. On the other hand, falls from heights often involve injuries to the hilar structures and perihilar parenchyma. Thus, a detailed approach focusing on the localization and qualitative differentiation of injuries in parenchymal organs, especially those associated with hilum or other fixation mechanisms, could significantly enhance the differential diagnosis process and warrants further investigation.

The analysis of skeletal fracture distribution in our cohort revealed significant differences in the prevalence of skull fractures. These fractures were commonly observed in both types of fatal events but were more frequent in falls from heights (p-value = 0.044). However, skull fractures are significantly influenced by the specific dynamics of the traumatic event. Due to the relatively small sample size, the observed differences might be due to random variation rather than indicating a true statistical difference. Further research into the spatial distribution of fractures, which was not addressed in this study, could yield additional insights.

Also, bilateral forearm fractures were notably higher in fall victims (7.0%) versus pedestrians (0.0%). On the other hand, unilateral leg fractures were significantly more common in pedestrians (28.2%) compared to falls from height (16.3%). Thus, the findings reaffirmed the validity of earlier observations regarding the laterality of fractures. Our research revealed that bilateral forearm fractures are exclusively associated with falls from heights. This finding supports the hypothesis that falls are associated with a higher frequency of frontal impacts, which may indicate a defensive posture adopted by the victims before hitting the ground.

Then, the statistical significance of the differences observed in unilateral leg fractures, which are more prevalent among pedestrians, underscores the likelihood of a lateral direct impact to the legs as a distinguishing factor in these incidents.

The literature generally does not differentiate between unilateral and bilateral lower limb injuries, often referring to them collectively as lower limb fractures. Research on vehicle-pedestrian collisions shows lower limbs involvement rates ranging from 24.2 to 52.5% [16, 24, 25]. In contrast, studies on falls from heights reveal lower rates of lower limb fractures, ranging from 6.3 to 29.8% [23, 26, 27]. Moreover, Teresinski et al. [28] reported a 30.5% incidence of foot bone fractures in individuals struck by vehicles, a rate significantly higher than the 2.9% observed in our study, with a complete absence of bilateral foot involvement.

Based on our earlier discussion of lung injuries, we expected to find differences in the frequency of bilateral rib fractures. However, such differences were not observed. This lack of disparity may be attributed to the fact that while bilateral lung injuries often result from significant deceleration forces, rib fractures are primarily caused by direct blunt trauma. Since direct blunt impact is a common factor in both falls from heights and car-pedestrian collisions, this explains the absence of significant differences in bilateral rib fractures between the two types of events, despite their higher frequency in falls from height (47.3% vs. 39.8%). However, it should be noted that the number of rib fractures was not considered in the current study, which could potentially provide additional insights for differential diagnosis.

A further aim of this study was the quantitative evaluation of specific variables, a novel approach that facilitates comparison, classification, and statistical analysis. Among the quantitative variables assessed, including pleural effusion, peritoneal effusion, pericardial effusion, and total skin injury, only the latter demonstrated statistically significant differences between deaths resulting from vehicle impacts and those from falls. The results indicated a significantly greater total injured skin surface area in pedestrians struck by cars compared to those who had fallen from heights. This finding reinforces the substantial disparity in external injuries between the two types of events.

In the current study, the “Total Injured Skin Area” threshold value of 84.2 cm², obtained through ROC analysis, represented the optimal cutoff for differentiating the cause of death. This figure might seem particularly low, especially considering that the maximum injury extent measured among pedestrians was 2637.7 cm², but it actually underscores the limited extent of external injuries recorded in cases of death due to falls from height. Among fall victims, moreover, the median total injured skin was 65.00 cm², against a median of 211.20 cm² for pedestrians. Therefore, our research suggests that injuries exceeding this threshold are likely indicative of pedestrian impacts.

However, further studies are needed to explore variables not analyzed in this preliminary research, such as fall height, impact with objects during descent, and vehicle speed. Future research could lead to the development of a diagnostic algorithm for forensic pathologists, providing a more reliable tool to differentiate between these two types of fatal events. Additionally, this study’s focus on both qualitative and quantitative data, including the patten of injuries and their mono- and bilaterality, offers promising insights that could enhance differential diagnosis. Expanding the sample size and refining the “Total Injured Skin Area” cutoff values will be crucial for integrating these findings into a comprehensive diagnostic tool.