Introduction

Forensic tissue mechanics describes the strategic biomechanical analysis of human tissues to obtain relevant information for criminal investigations [1]. With regard to time since death estimation, tissue mechanical analyses show promise beyond the post-mortem intervals (PMIs) covered by the routinely applied temperature-based Henssge method [2, 3]. The Henssge method is no longer applicable once body temperature and ambient temperature reach equilibrium, which depends on several factors, including the body mass index and the body surface area [4]. In contrast, rheological analyses of human brain tissue have proven useful for PMIs of up to 10 days at constant post-mortem ambient temperatures of 4 °C [5]. To date, brain [5] and liver tissues [6] are the only human organs that were analysed according to the principles of forensic tissue mechanics after the method had been established on ovine tissues [7–9]. A fundamental hypothesis of forensic tissue mechanics is that, under identical storage conditions, the biomechanical properties of each human organ change in a characteristic, time-dependent manner. Consequently, combining biomechanical properties from different organs is likely superior to analysing only a single organ per case when estimating time since death based on tissue mechanical analyses.

The spleen is an easily accessible and routinely examined parenchymatous organ at autopsy; however, to date it has been of minor forensic relevance [10]. Spleen palpation is a routine step during autopsy and enables the forensic pathologist to obtain observer-dependent, qualitative information about the biomechanical state of the organ. On palpation, a soft or “muddy” spleen with decreased firmness is a common sign of sepsis [11]. To date, only a few biomechanical studies have investigated post-mortem human spleen samples [12, 13]. Despite the routine examination of the spleen at autopsy, its biomechanical properties have never been systematically evaluated as a marker for time since death estimation or cause of death determination.

This study aims to perform a rheological analysis of post-mortem human spleen samples and to assess their applicability for time since death estimation and diagnostic questions relevant to routine forensic practice. To this end, the rheological properties of the spleen were assessed in a forensic autopsy cohort and related to PMI, age at death, spleen weight, sex, initiated resuscitation measures, and microscopic findings in spleen samples.