Postmortem Interval Estimation from Bone Marrow Lipids

As submitted by the proposer:

In forensic contexts, the accurate estimate of the postmortem interval (PMI) can mean the difference between a positive identification and a cold case. The majority of scientific literature that describes postmortem processes focuses on soft tissue decomposition and does not address bone degradation. Methods currently available to estimate PMI in severely decomposed or skeletonized remains use descriptive data and provide broad, often unusable estimates that are not well validated and lack known error rates.

This study uses analytical data from cadaveric tissue metabolites to provide a validated quantitative method with known predictive value and error for determining PMI of skeletal remains—a standard that is not currently available to practitioners. By utilizing biomarkers related to regular, predictable tissue breakdown, we anticipate that this method will also provide a means of overcoming the geographic limitations of methods based on subjective observations of gross morphological changes.

Wood and Shirley (2013) demonstrated that phospholipids and fatty acids in human muscle cell membranes have high predictive capacity for PMI estimation. We expand this metabolomic and lipidomic analysis to bone to provide a quantitative method for estimating PMI after soft tissues have decomposed and only bone remains. High resolution mass spectrometry will be used to analyze bone samples for time-dependent biomarkers related to postmortem degradation of bone.

Bone samples will be derived from two sources: remains placed at the UT Anthropology Research Facility (ARF) and skeletal remains in the William M. Bass Donated Collection. The LMU Metabolomics Unit will analyze the samples for biomarkers that are strongly correlated with postmortem interval. Bone plugs will be collected at regular intervals from the proximal tibia of 20 cadavers at ARF for two years to represent a serial sample. A second sample will be taken from 100 skeletons in the Bass Collection with known PMIs of 1-to-30 years to expand the capacity of the method to estimate long term PMI.

Once the most consistently extracted biomolecules are identified, multiple regressions will be used to develop equations for predicting PMI that can be used by forensic practitioners. An additional 30 bone samples will be collected from Bass Collection skeletons to perform a validation study and test these equations. This work will provide a quantitative method for forensic practitioners to estimate long-term PMI from partially or completely skeletal remains using biomarkers unique to the decomposing corpse as opposed to subjective visual observations of bony diagenesis.

Note: This project contains a research and/or development component, as defined in applicable law, and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14).

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