Two-dimensional linear analysis of dynamic bare footprints: A comparison of measurement techniques

A preliminary study on the stability of bare footprint linear measurements in four motion states

In some crime scenes, there may be bare footprints. Analyzing and testing the linear measurements of bare footprints in crime scenes can play an important role in personal analysis and individual identification. However, the linear measurements of bare footprints may be influenced by different motion states, leading to changes in length and width or even significant deviations. Previous studies focused on the linear differences between static and dynamic footprints, and failed to take the speed factor into consideration. This paper studied the stability and change regularities of the linear measurements of bare footprints in four different motion states: standing, normal walking, fast walking and trotting. Dust footprints of the right feet were collected from 80 healthy young adults under these four motion states. Seven linear measurements were obtained for each footprint using the Reel method, totaling 2240 data sets. One-way repeated measures ANOVA was used to assess the measurement variations across the four states. The results showed that there were statistically significant variances in the length measurements (A1-A5) between the standing state and other motion states, whereas no statistically significant variances were observed between the three dynamic states. It was found that the mean values of the five length measurements (A1-A5) increased from static to dynamic state, and then gradually decreased slightly as the walking speed increased. Additionally, no significant differences were found in the two width measurements (MPJ Width and Calc Width) between the four motion states. As a preliminary study, this study can provide a reference for the analysis of bare footprints in different motion states extracted from crime scenes.

The importance of assessing the ghosting phenomenon in dynamic footprints when estimating stature - Forensic implications

In cases where multiple footprints are found at a crime scene, it is unusual that all are static, and some are likely dynamic. Depending on how the footprint was made, we distinguish between dynamic and static footprints. A distinguishing feature that has only recently been associated with dynamic footprints is the fact that dynamic footprints differ from static footprints by the presence of additional markings around the back of the heel and the tops of the toe prints, the so-called ghosting phenomenon. The present study aims to analyse the ghosting phenomenon on dynamic footprints - its occurrence in relation to sex, laterality, and different areas of footprints as well as length features. Additionally, it aims to investigate the assessment of the ghosting phenomenon on dynamic footprints when estimating stature for biological profiling in the forensic field. The study sample comprised of 170 young adults aged 18 - 30 years of both biological sexes. Stature was measured and dynamic footprints were obtained where the ghosting phenomenon was analysed together with length measurements of the same footprint with and without ghosting. In the first and second toes of footprints, the ghosting phenomenon occurred most frequently in both sexes and in the sex-mixed group. Sex differences were not significant in ghosting occurrence on right and left footprints (p > 0.05), except for the area of the left fifth toe (p = 0.045). All the footprints' lengths with ghosting were significantly higher (p < 0.001) than those without ghosting. Statures calculated from footprint length measurements with ghosting predicted stature more accurately than statures calculated from the same footprint length measurements without ghosting. In the case of finding dynamic footprints at crime scenes, it is necessary to correctly identify and evaluate ghosting of the footprint. This comparison can be helpful in interpreting how ghosting should be taken into account when estimating a person's stature.

Forensic measurement comparison of foot insole impressions

In forensic podiatry, footprints have been shown to provide a valuable source of discriminatory information. Footprints may be found in various forms, such as bare footprints, sock-clad footprints, or as impressions on insoles within footwear. This study utilized quantitative measures of foot impressions on pairs of insoles from shoes worn by the same person from a population of 31 adults. The measurements were determined by using the Reel method and comprised measurements from the heel to the tips of the toes and width of the ball. The purpose of the study was to assess the margin of error for these measurements to determine whether they were sufficiently accurate for forensic use. A secondary purpose of this study was to determine whether the analyst's experience or lack thereof in forensic podiatry had an impact on the precision of measurement data. The insole foot impressions were assessed by two podiatrists with forensic podiatry experience in footprint analysis, footprint research, and in using the Reel method of footprint measurement, as well as by three students of podiatric medicine without any such experience. A statistical analysis of the data from the study was performed using SPSS v28 (IBM SPSS Statistics for Windows, Version 28.0. Armonk, NY: IBM Corp). The most reliable measurements were of forefoot width, heel to first toe, heel to second toe, and heel to fourth toe. The greatest variation occurred in the measurements of the heel to the third and fifth toes. The measurements of the forensic podiatrist analysts showed less variability than those of the podiatry students, suggesting that measurement precision is related to the experience of the analyst.

Ghosting phenomenon in static and dynamic footprints in India and the United States

Ghosting is the phenomenon that exists when a footprint has a lighter area around the tip of one or more toes or a shadow-like area at the back of the heel. To date, ghosting has been considered primarily a finding of dynamic (walking) footprints, rather than static (standing) footprints. The prevalence of ghosting in static footprints is unknown, and research on its presence in static and dynamic footprints from the same participant is sparse, as are studies on its occurrence in different geographic populations. This study is among the first to evaluate the occurrence of ghosting in the static and dynamic footprints from a particular individual with participants in two geographic populations. A combination of both inkless and ink footprint collection systems were used to obtain a total of 206 bare footprints from 103 adult participants from the United States and India. The data comprised 103 static and 103 dynamic footprints. Ghosting occurred significantly in static footprints, though less frequently than in dynamic footprints. Ghosting in static footprints was seen most often at the first toe, followed by the third and second respectively. This aspect appeared least at the heel. In dynamic footprints, it occurred most at the first toe, followed by the second and fourth toes, and then the third toe and the heel. The prevalence of ghosting in footprints from the United States and India differed in their locations, notably at the first and second toes in the static footprints and at the heel in the dynamic footprints.

One size fits all? Stature estimation from footprints and the effect of substrate and speed on footprint creation

Estimation of stature from footprint lengths is a common prediction in forensic cases and in paleoanthropology upon the discovery of fossil footprints. Many studies, which have estimated stature from footprints, generally use a "one-size-fits-all" approach that usually involves applying a known ratio of foot length to total stature to do so, although this method has fallen out of practice in forensic cases in recent years but is still commonly used for fossil trace evidence. Yet, we know that substrate and speed can change the dimensions of a footprint, so why are these "one-size-fits-all" approaches still used today? We tested footprint production across different substrates at a walk, a fast walk, and a jog. We calculated how accurately footprint dimensions were impressed between these different conditions and identified sources of error in footprint lengths, and the percentage changes of how significantly a footprint can change in length between different conditions. We provide a table with different ratios that we encourage practitioners/field scientists to refer to and use when estimating stature from footprints, with respect to the substrate on which the footprint was created and the speed at which it was created. We actively encourage researchers to add the ratios by testing more substrates so that in the future stature can be more accurately estimated, thus aiding the paleoanthropological community, but also forensic investigations by statistically highlighting how different conditions can affect trace dimensions.

Estimation of stature and body weight from static and dynamic footprints - Forensic implications and validity of non-colouring cream method

In the present study, the metric properties of dynamic footprints were analysed using non-colouring method in relation with body parameters and compared with static footprint measurements. The results of the study provide a better understanding of the relationship between static and dynamic footprints, which may be useful for biological profiling that allows more accurate identification. Stature, body weight, five length and two width parameters of dynamic (walking) footprints of young Slovak adults (65 females and 68 males) were analysed. Pearson correlation coefficients were calculated and equations for prediction of stature and body weight by linear regression analysis and multiple regression analysis were developed. Intersex differences were confirmed for all parameters and bilateral for some. Statistically significant differences were found in all measurements (p-value>0.05), except for the width of the standing and walking footprint in the mixed group. A positive correlation was found between the selected footprint diameters with stature (max - r = 0.82) and body weight (max - r = 0.70). Stature could be calculated with an accuracy of up to 4.40 cm and body weight with an accuracy of up to 9.56 kg. The results of the present study show that selected measurements of dynamic footprints correlate with stature and body weight. These results could be used in biological profiling in the medical and forensic fields.

Application of non-contact scanning to forensic podiatry: A feasibility study

Foot impression evidence recovered from crime scenes can be available in the form of barefoot prints, sock-clad footprints, or as impressions within footwear. In some cases, suspects leave their footwear at the scene of the crime, and the insoles from the footwear can be important in linking a person to the footwear. The application of 3D data-collecting technology is becoming more and more popular within forensic science and has been used to recover footwear impression evidence. The present study is a feasibility study to discover if 3D data capturing devices can be applied to insoles; to capture the footprint impression for measurement using the Gunn method (a method used in forensic podiatry casework). Three different methods of data capture were conducted; Adobe Photoshop, MeshLab, and calipers used directly on the insole. Paired t-tests and Intraclass Correlation Coefficient (ICC) were conducted for all three data capture methods. Seven measurements used in this study were significantly different across all three methods. ICC scores were moderate to excellent for the Photoshop method, poor to good for the 3D method, and moderate to excellent for the Direct method.

Chasing ghosts: An investigation of the ghosting phenomenon in footprints

Ghosting is a phenomenon that has been identified in dynamic (walking) footprints. There is sparse research on the occurrence of ghosting; however, due to the forensic value of footprints and their use in other scientific fields, the phenomenon of ghosting warrants further study. Ghosting can be used to determine if a footprint is static (standing) or dynamic, which can help forensic investigators create a sequence of events at a crime scene. Furthermore, this can help in footprint comparisons from this determination, as "like versus like" comparisons of dynamic or static footprints can be made. The purpose of this research was to determine the prevalence and locations of the ghosting phenomena in dynamic footprints. 136 dynamic footprints from 68 volunteers were collected using an inkless collection system. Each footprint was visually inspected for ghosting as well as examined using software. Ghosting was present on at least one location in all footprints. The highest prevalence occurred at the tip of the great toe, followed by the second digit and the heel. To a lesser extent, ghosting appeared at the tips of the other three digits. Ghosting often occurred at two or more areas in a given footprint.

Heuristic Analysis for In-Plane Non-Contact Calibration of Rulers Using Mask R-CNN

Determining an object measurement is a challenging task without having a well-defined reference. When a ruler is placed in the same plane of an object being measured it can serve as metric reference, thus a measurement system can be defined and calibrated to correlate actual dimensions with pixels contained in an image. This paper describes a system for non-contact object measurement by sensing and assessing the distinct spatial frequency of the graduations on a ruler. The approach presented leverages Deep Learning methods, specifically Mask Region proposal based Convolutional Neural Networks (R-CNN), for rulers’ recognition and segmentation, as well as several other computer vision (CV) methods such as adaptive thresholding and template matching. We developed a heuristic analytical method for calibrating an image by applying several filters to extract the spatial frequencies corresponding to the ticks on a given ruler. We propose an automated in-plane optical scaling calibration system for non-contact measurement.

Two-dimensional metric comparisons between dynamic bare footprints and insole foot impressions-forensic implications

Footwear may be found at crime scenes as physical evidence. Such footwear often has impression features of the wearer's foot on the insole of the shoe. Scientific research and literature have established that footprints are distinct. This study compares two-dimensional measurements on bare footprints to foot impressions on insoles to determine if significant differences or similarities exist. Dynamic footprints were collected from 51 donors using theIdenticator® Inkless Shoe Print Model LE 25P system. Seven foot length and width measurements were taken based on the Reel linear measurement method. Footprint measurements between bare footprints and foot impressions on the insoles were compared. Only two differences (p > 0.05) were observed between the various bare footprint and insole foot impression measurements on the right and left side for most of the measurements, CALC (p < 0.001) and A1 (p = 0.04). Bare footprint and insole A5 measurements on the left side were also significantly different (p = 0.015). The results of the study have implications in the forensic analysis of foot impression evidence on insoles in footwear in assisting with identifying the wearer of said footwear. Situations may arise in the forensic context when comparing the foot impression on the insole of footwear to a suspect's bare footprint or a footprint from post-mortem remains. This study contributes to the scant literature available on the topic and to understanding the similarities and differences observed in the various linear measurements that may be utilized in the comparison process of footprint impressions on shoe insoles to bare footprints.