SGER: Biomechanical Modeling to Forensic Estimation of Time Since Death

The University Of Central Florida Board Of Trustees, Orlando FL

Investigators

Abstract

Biomechanical Modeling to Forensic Estimation of Time Since Death Abstract This proposal is designed to address the question: "Can the time of death for a human be estimated from measured changes in mechanical material properties of specific tissues post-mortem?" A multidisciplinary team, consisting of a Forensic Anthropologist, an Anatomist and a Mechanical Engineer, has been formed to attempt to answer this question. Since this research is at such a preliminary stage the NSF "Small Grants for Exploratory Research" is the appropriate mechanism for initial funding of the project. To gain insight into the mechanical degradation of human tissue after death, the tissue must be chosen from a location in the body which decomposes at a relatively slow rate. Because of tissue encapsulation, we have chosen intervertebral discs (annulus fibrosus) in the spine as the most likely test specimens for this study, however, other tissues (e.g. teeth) will be considered as the testing protocol is developed. Initially, three (limited by cost) human vertebral columns will be harvested from fresh (unpreserved) cadavers for which time of death is known. The intervertebral discs will be surgically extracted from the thoracic and lumbar regions of the spinal columns at specified time intervals. These harvested discs will be described macroscopically and microscopically, then mechanical material properties will be determined from quasi-static, dynamic and time-dependent compression testing imposed by an Instron 8511 Mechanical Testing Machine. Additionally, pilot studies using ultrasound techniques will be investigated. The load and deformation data acquired from the mechanical tests will be modeled using the power law, exponential law, homography or other applicable constitutive laws appropriate for biological material to determine material parameters at specific times since death. It is expected that a trend between the material parameters and time since death will emerge.