# Comparative Analysis of LiDAR and Photogrammetry for 3D Crime Scene Reconstruction
## 4 Results and Discussion
### Discussion  
This study evaluates LiDAR and photogrammetry in indoor crime scene scenarios while highlighting their effectiveness in creating 3D models for forensic analysis. Like the findings of [PERSON] et al. [31], our study confirms that handheld LiDAR devices like those found in mobile phones can swiftly and effectively capture crime scenes. Our findings support their results on how LiDAR scanners can achieve acceptable precision levels for crime scene investigations. Furthermore, the swift documentation ability highlighted by [PERSON] et al. [7] was also evident in our results, showing how iPhones with LiDAR scanners can efficiently gather point clouds under optimal lighting conditions.  
However, despite the fast data acquisition, there exist challenges with LIDAR in terms of sensitivity to various lighting conditions, affecting collected data integrity as well as efficiency, resulting in missing point clouds, as shown in the different scans where several point clouds were missing. Our observation about the limited details of the crime scene and the discrepancies in the color and alignment in low-light conditions raises concerns, like those in a study by [PERSON] and [PERSON] [9], which should be taken into consideration when trying to interpret LiDAR data in forensic investigations. While our study did not explicitly focus on the accuracy of closeup scans of evidence found at crime scenes, we did scan a small area covering a few objects of interest, a footprint, spatters of blood, and scissors, all found in our mock-up crime scene, as shown in Figure 8. With a single scan attempt using Recon-3D with 1 mm resolution, the scan took 1 min with 1.9 M point clouds. This resulted in obtaining the highest-possible resolution details achievable by the application, with only  
Figure 7: Cloud-to-cloud distance heatmap (in meters) (**left**) and related histogram showing most point clouds (90%) fall under 0.12m of error (**right**). The regions of high errors are from the sensing boundary or blind spots during the scanning.  
a few point clouds missing at the scan corners. Still, the objects of interest in the scene were fully reconstructed in 3D. This close-up reconstruction will be particularly effective in outdoor scenes such as muddy ground where 3D reconstruction of evidence is critical.  
Also, it should be mentioned that the visual representations sometimes showed discrepancies across the different areas in the maps, resulting in shadows and some objects not aligned properly, as shown in Figure 9. Maintaining the integrity of 3D models is also critical when dealing with criminal cases. Our research incorporates LiDAR and photogrammetry technologies for their accuracy in capturing crime scene details, thus reducing the chances of tampering with data during the investigation process. According to [PERSON] and [PERSON] [5], the accuracy of these reconstructions is essential, as any unauthorized changes or contamination in data quality could affect their admissibility as evidence in the courtroom. In addition, digital documentation of crime scenes not only assists first responders when dealing with crime scenes but also helps in preserving the collected evidence integrity for further investigation, which usually comes in handy in later proceedings. According to [PERSON] et al. [6], incorporating 3D digital tools in law enforcement enhances the durability of crime scene documentation by enabling examinations beyond the initial phase of crime scene documentation. This feature proves vital when preserving the physical crime scene, which is not feasible over time. An equally important aspect is the incorporation of the hashing mechanisms, such as MD5 or SHA1, to preserve the integrity of the 3D digital map obtained. This will ensure the Chain of Custody of the 3D reconstructed maps.  
Figure 8: A 3D reconstructed footprint as a piece of evidence at the scene.  
Figure 9: Failed image alignments in a marker on the floor and an April Tag on the wall (with arrows).