The Eye in Forensic Medicine: A Narrative Review

The eye in forensic practice: In the living

Eye examination plays an important role when living individuals are forensically investigated. The iris colour, retinal scans and other biometric features may be used for identification purposes while visual impairments may have legal implications in employment, driving and accidents. Ocular manifestations provide clues regarding substance abuse, poisoning and toxicity, and evidence of trauma, abuse or disease can be revealed along with psychological traits and lifestyle. Thus, the eye is a valuable tool in forensic investigations of living subjects, providing identifying characteristics along with health information. This review focuses on the medico-legal aspects of the eye's contribution when the living are subjected to forensic examination.

Postmortem changes in the eye on computed tomography images

BACKGROUND

Ocular tension decreases with increasing postmortem interval (PMI) and eyes collapse with extreme progression of postmortem change; however, time-related changes in postmortem computed tomography (PMCT) findings have not been clarified. This study aimed to quantitatively evaluate the vitreous volume and CT values of the vitreous body to clarify time-related changes in PMCT.

METHODS

We retrospectively reviewed PMCT images of the eyes of subjects who underwent autopsy at our institution between July 2023 and February 2024. They were classified into four PMI groups: PMI-1: < 1 day, PMI-2: 1-2 days, PMI-3: 3-6 days, PMI-4: ≥ 7 days. The vitreous volumes and mean CT values of the vitreous chambers were measured. Additionally, the presence of intraocular gas and crystalline lens dislocation was observed.

RESULTS

The PMCT images of 131 eyes of 66 patients (41 males, 25 females) were analyzed. The mean age was 63.7 (22-99) years. The volume of the vitreous cavity was significantly decreased at PMI-3 and PMI-4, which indicated scleral depression. Intraocular gas appeared in PMI-4. Lens dislocation began at PMI-3 and was more frequently observed at PMI-4 and in the higher-temperature environment group.

CONCLUSION

Ocular findings on PMCT are useful for estimating the time of death.

Postmortem sympathomimetic iris excitability

BACKGROUND

A reliable estimation of time since death can be important for the law enforcement authorities. The compound method encompassing supravital reactions such as the chemical excitability of the iris can be used to further narrow intervals estimated by temperature-based methods. Postmortem iris excitability was mostly assessed by parasympatholytic or parasympathomimetic substances. Little is known regarding sympathomimetic agents. The present study aims to describe the postmortem iris excitability using the sympathomimetic drug phenylephrine.

METHODS

Cadavers were included after body donors gave written informed consent during lifetime. Exclusion criteria were known eye disease, or a postmortem interval exceeding 26 hours. A pupillometer with a minimum measurement range of 0.5 mm was used to determine the horizontal pupil diameter before and 20 minutes after the application of phenylephrine. Increase in pupil diameter was labeled as positive reaction, unchanged pupil diameter was labeled as negative reaction, and decrease in pupil diameter was labeled as paradox reaction.

RESULTS

30 eyes from 16 cadavers (median age = 80.0; 9 males, 7 females) were examined. Initial pupil size was in median 3.5 mm (interquartile range [IQR]: 3.0-4.5 mm) and progressed to 4.0 mm (IQR: 3.5-5.0 mm) 20 minutes after drug instillation. The achieved pupil diameter difference comprised in median 0.5 mm (IQR: 0.0-1.0 mm). A positive reaction was observed in 21 cases. Negative reactions were observed in 5 cases and paradox reactions in 4 cases. Overall, there was a statistically significant difference in diameter between the initial and the reactive pupil (P = 0.0002).

CONCLUSION

Although relatively rarely used, sympathomimetic drugs seem to be eligible for chemical postmortem iris excitability. Currently, assessment of postmortem iris excitability usually only involves parasympatholytic and parasympathomimetic agents. The findings of the present study give a hint that the application of a third agent with a sympathomimetic mechanism of action could provide additional information. Further studies assessing such a triple approach in the compound method in comparison with the current gold standard for estimation of time since death are mandatory to ensure reliable results.

The eye in forensic practice: In the dead

Post-mortem examination of the eye provides valuable forensic information yet is often overlooked. This brief review focuses on determining the cause/manner of death and post-mortem interval. External eye findings like corneal haziness and tache noire, combined with post-mortem changes in the iris, lens, retina and vitreous humour, can help estimate time since death. Ocular biometrics (iris/retinal scans) may facilitate identification. Age-related ocular changes can provide insights. The eye offers clues into personality (corneal tattooing, trichotillomania) and cause of death (petechiae in strangulation, retinal haemorrhages in abusive head trauma). Ocular trauma and underlying eye disease may be evident. Toxicology of vitreous humour can detect drugs/poisons. As a window into systemic disease and age-related changes, the eye aids pathology interpretations and, accordingly, post-mortem examinations have value. Ocular findings should not be overlooked in forensic examinations as they provide distinct information in determining cause/manner of death and post-mortem interval.

A Mini-review on New Developments in Nanocarriers and Polymers for Ophthalmic Drug Delivery Strategies

The eye is an important and vital organ of the human body consisting of two segments - anterior and posterior segments and these segments are associated with many diseases. This review elaborates upon the various eye-related diseases with their medications and carriers used to deliver them. Delivery strategies include drugs encapsulated into liposomes, polymeric micelles of drugs, solid lipid nanoparticles, nanostructured lipid carriers, nano emulsions, and Nanosuspension used to improve penetrating properties, bioavailability, and residence time of the drugs as examples available in the literature. With regard to this, different forms of ocular drug delivery are classified and elaborated. Additionally, the possibility of addressing the physical and chemical complexities of ocular diseases and how they could be overcome with environmentally stable nanoformulations are briefly discussed. Enhanced drug delivery efficiency with various novel pharmaceuticals along with enhanced uptake by different routes/modes of drug administration. Current advancements in drug carrier systems, i.e., nanocarriers, have shown promise for improving the retention time, drug permeation and prolonging the duration of release of the drug in the ocular site. Bio-degradable polymers investigated for the preparation of nanocarriers for the entrapment of drugs and to enhance the efficacy through improved adherence of tissue in the eye, sustained release measures, enhanced bioavailability, lower toxicity, and targeted delivery is applicable. This review covers the introduction of various nanocarriers and polymers for ocular drug delivery with the purpose of enhancing the absorption, retention and bioavailability of medications in the eye.

Metabolomics investigation of post-mortem human pericardial fluid

INTRODUCTION

Due to its peculiar anatomy and physiology, the pericardial fluid is a biological matrix of particular interest in the forensic field. Despite this, the available literature has mainly focused on post-mortem biochemistry and forensic toxicology, while to the best of authors' knowledge post-mortem metabolomics has never been applied. Similarly, estimation of the time since death or post-mortem interval based on pericardial fluids has still rarely been attempted.

OBJECTIVES

We applied a metabolomic approach based on 1H nuclear magnetic resonance spectroscopy to ascertain the feasibility of monitoring post-mortem metabolite changes on human pericardial fluids with the aim of building a multivariate regression model for post-mortem interval estimation.

METHODS

Pericardial fluid samples were collected in 24 consecutive judicial autopsies, in a time frame ranging from 16 to 170 h after death. The only exclusion criterion was the quantitative and/or qualitative alteration of the sample. Two different extraction protocols were applied for low molecular weight metabolites selection, namely ultrafiltration and liquid-liquid extraction. Our metabolomic approach was based on the use of 1H nuclear magnetic resonance and multivariate statistical data analysis.

RESULTS

The pericardial fluid samples treated with the two experimental protocols did not show significant differences in the distribution of the metabolites detected. A post-mortem interval estimation model based on 18 pericardial fluid samples was validated with an independent set of 6 samples, giving a prediction error of 33-34 h depending on the experimental protocol used. By narrowing the window to post-mortem intervals below 100 h, the prediction power of the model was significantly improved with an error of 13-15 h depending on the extraction protocol. Choline, glycine, ethanolamine, and hypoxanthine were the most relevant metabolites in the prediction model.

CONCLUSION

The present study, although preliminary, shows that PF samples collected from a real forensic scenario represent a biofluid of interest for post-mortem metabolomics, with particular regard to the estimation of the time since death.

Clinical and Forensic Investigation Protocols for Diagnosing Abusive Head Trauma: A Literature Review

Abusive head trauma (AHT) represents a very serious global public health problem. Prevention of these episodes is essential to reduce the morbidity and mortality of this phenomenon. All healthcare professionals should be able to recognize the signs of abuse. However, diagnosis is very complex as the signs are often blurred and cannot be recognized with certainty without carrying out adequate instrumental investigations. It has been calculated that approximately one-third of AHT cases remain undetected and require more than one medical visit to be correctly interpreted and diagnosed. On the other hand, the literature has recently also emphasized the problems related to possible false diagnoses of abuse and the numerous family and personal repercussions that follow from this issue. For these reasons, correct and timely recognition is essential to avoid the risk of recurrence of AHT and to start proper forensic investigations, in order to identify the offender or exonerate a suspect. The present work explores the most recent evidence of recent years in the field of AHT diagnostics through a literature review. The purpose of this article is to provide forensic pathologists with clear tools for diagnosis based on the literature. To this end, the review suggests clinical and forensic protocols aimed at the timely diagnosis of AHT in order to prevent abuse from remaining undetected.

The amino acid metabolomics signature of differentiating myocardial infarction from strangulation death in mice models

This study differentiates myocardial infarction (MI) and strangulation death (STR) from the perspective of amino acid metabolism. In this study, MI mice model via subcutaneous injection of isoproterenol and STR mice model by neck strangulation were constructed, and were randomly divided into control (CON), STR, mild MI (MMI), and severe MI (SMI) groups. The metabolomics profiles were obtained by liquid chromatography-mass spectrometry (LC-MS)-based untargeted metabolomics. Principal component analysis, partial least squares-discriminant analysis, volcano plots, and heatmap were used for discrepancy metabolomics analysis. Pathway enrichment analysis was performed and the expression of proteins related to metabolomics was detected using immunohistochemical and western blot methods. Differential metabolites and metabolite pathways were screened. In addition, we found the expression of PPM1K was significantly reduced in the MI group, but the expression of p-mTOR and p-S6K1 were significantly increased (all P < 0.05), especially in the SMI group (P < 0.01). The expression of Cyt-C was significantly increased in each group compared with the CON group, especially in the STR group (all P < 0.01), and the expression of AMPKα1 was significantly increased in the STR group (all P < 0.01). Our study for the first time revealed significant differences in amino acid metabolism between STR and MI.

PMI estimation through metabolomics and potassium analysis on animal vitreous humour

INTRODUCTION

The estimation of post-mortem interval (PMI) remains a major challenge in forensic science. Most of the proposed approaches lack the reliability required to meet the rigorous forensic standards.

OBJECTIVES

We applied ¹H NMR metabolomics to estimate PMI on ovine vitreous humour comparing the results with the actual scientific gold standard, namely vitreous potassium concentrations.

METHODS

Vitreous humour samples were collected in a time frame ranging from 6 to 86 h after death. Experiments were performed by using ¹H NMR metabolomics and ion capillary analysis. Data were submitted to multivariate statistical data analysis.

RESULTS

A multivariate calibration model was built to estimate PMI based on 47 vitreous humour samples. The model was validated with an independent test set of 24 samples, obtaining a prediction error on the entire range of 6.9 h for PMI < 24 h, 7.4 h for PMI between 24 and 48 h, and 10.3 h for PMI > 48 h. Time-related modifications of the ¹H NMR vitreous metabolomic profile could predict PMI better than potassium up to 48 h after death, whilst a combination of the two is better than the single approach for higher PMI estimation.

CONCLUSION

The present study, although in a proof-of-concept animal model, shows that vitreous metabolomics can be a powerful tool to predict PMI providing a more accurate estimation compared to the widely studied approach based on vitreous potassium concentrations.

Keep an eye on the crime – a new look at the forensic use of post-mortem eye examination to estimate time of death

Determining the time of death plays a crucial role in a forensic post-mortem examination. Many methods for the time of death (TOD) determination have been developed. However, most are not applicable during the first hours after death and produce large post-mortem interval (PMI) ranges. Eye examination makes it possible to precisely determine the time of death during the initial period after death with half-hour accuracy.. In recent years methods for estimating the time of death by measuring the changes in the eye have made great strides. Those methods use the changes in the reaction to drugs and macroscopically visible morphological changes. Experimental studies also produced equations that can estimate the post-mortem interval using biochemical, electrochemical and thermal changes within the eye.

Post-Mortem Interval and Microbiome Analysis through 16S rRNA Analysis: A Systematic Review

The determination of the Post-Mortem Interval (PMI) is an issue that has always represented a challenge in the field of forensic science. Different innovative approaches, compared to the more traditional ones, have been tried over the years, without succeeding in being validated as successful methods for PMI estimation. In the last two decades, innovations in sequencing technologies have made it possible to generate large volumes of data, allowing all members of a bacterial community to be sequenced. The aim of this manuscript is to provide a review regarding new advances in PMI estimation through cadaveric microbiota identification using 16S rRNA sequencing, in order to correlate specific microbiome profiles obtained from different body sites to PMI. The systematic review was performed according to PRISMA guidelines. For this purpose, 800 studies were identified through database searching (Pubmed). Articles that dealt with PMI estimation in correlation with microbiome composition and contained data about species, body site of sampling, monitoring time and sequencing method were selected and ultimately a total of 25 studies were considered. The selected studies evaluated the contribution of the various body sites to determine PMI, based on microbiome sequencing, in human and animal models. The results of this systematic review highlighted that studies conducted on both animals and humans yielded results that were promising. In order to fully exploit the potential of the microbiome in the estimation of PMI, it would be desirable to identify standardized body sampling sites and specific sampling methods in order to align data obtained by different research groups.