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PMICALC: an R code-based software for estimating post-mortem interval (PMI) compatible with Windows, Mac and Linux
José I Muñoz-Barús1, María Sol Rodríguez-Calvo, José M Suárez-Peñaranda
1Institute of Legal Medicine, University of Santiago de Compostela, C/ San Francisco sn, 15782 Santiago de Compostela, Spain. joseignacio.munoz.barus@usc.es
Abstract:
In legal medicine the correct determination of the time of death is of utmost importance. Recent advances in estimating post-mortem interval (PMI) have made use of vitreous humour chemistry in conjunction with Linear Regression, but the results are questionable. In this paper we present PMICALC, an R code-based freeware package which estimates PMI in cadavers of recent death by measuring the concentrations of potassium ([K+]), hypoxanthine ([Hx]) and urea ([U]) in the vitreous humor using two different regression models: Additive Models (AM) and Support Vector Machine (SVM), which offer more flexibility than the previously used Linear Regression. The results from both models are better than those published to date and can give numerical expression of PMI with confidence intervals and graphic support within 20 min. The program also takes into account the cause of death.
Insights
Estimating time of death using vitreous humor chemistry is improved with PMICALC software. This R package uses Additive Models and Support Vector Machines for more accurate post-mortem interval (PMI) calculations.
Area of Science:
- Forensic Science
- Biochemistry
- Computational Biology
Background:
- Accurate post-mortem interval (PMI) estimation is crucial in legal medicine.
- Previous methods using vitreous humor chemistry and linear regression yielded questionable results.
- Advances in computational methods offer potential for improved PMI determination.
Purpose of the Study:
- To present PMICALC, an R package for estimating PMI in recent deaths.
- To evaluate the efficacy of Additive Models (AM) and Support Vector Machines (SVM) for PMI estimation using vitreous humor analytes.
- To provide a user-friendly tool for forensic practitioners.
Main Methods:
- Vitreous humor samples analyzed for potassium ([K+]), hypoxanthine ([Hx]), and urea ([U]) concentrations.
- PMI estimated using two regression models: Additive Models (AM) and Support Vector Machine (SVM).
- PMICALC software developed in R, incorporating cause of death into calculations.
Main Results:
- Both AM and SVM models provided more accurate PMI estimations compared to previous linear regression methods.
- The PMICALC package offers numerical PMI expression with confidence intervals and graphic support.
- Results are available within 20 minutes, improving efficiency in forensic investigations.
Conclusions:
- PMICALC provides a significant advancement in post-mortem interval estimation.
- The use of AM and SVM models enhances the reliability and accuracy of vitreous humor chemistry for PMI determination.
- This freeware package offers a valuable tool for legal medicine, improving the accuracy and speed of time of death determination.
