Dr Christopher Rogers, Faculty of Science & Engineering

Christopher joined the University of Wolverhampton as a Senior Lecturer in Forensic Science in May 2016. His previous roles included working as a Lecturer/Senior Lecturer at Glyndwr University (Wales), a Visiting Fellow at the Institute of Forensic Research (Instytut Ekspertyz Sądowych) in Krakow Poland, a Histologist (NHS Histopathology Department), and a Physical Anthropologist at the Natural History Museum (London).

The crystal maze – finding the way to a new method in post-mortem interval estimation

Introduction/Background  

After an organism dies, it decomposes – this involves a series of processes that have occurred since life first evolved on earth. Surprisingly however, we know very little about how and why things actually break down after death. This lack of knowledge is of serious concern in forensic investigations involving decomposed remains, especially when questions relating to how long somebody has been dead arise.

Forensic taphonomy is a relatively new discipline that aims to study, amongst other things, how remains decompose and how this information can assist in determining the post-mortem interval (PMI) (e.g. Haglund and Sorg, 1997, 2002, Vass, 2001). Many methods used to determine the PMI are not suitable for use on remains that have been dead for more than 48 hours due to the progression of post-mortem changes – this highlights the need to understand the decomposition process in much greater detail. The processes of decomposition are directly influenced by the environment in which the body is found, with temperature, moisture, oxygen availability, and access by insects/scavengers being important factors (e.g. Vass, 2001). Determining the PMI of buried remains is a particular challenge with a lack of suitable accurate methods (Rogers et al, 2011, 2014).

The development of new techniques is essential and requires novel ways of thinking, including assessing areas of anatomy that are overlooked in the forensic arena. This school of thought has already resulted in successful results by analysing cartilage in buried remains (Rogers et al, 2011, 2014). This research found that after death, in burial situations, crystals are produced by bacteria on the surface of articular cartilage found in pig remains between 3-6 weeks post-mortem – thus providing a PMI methods for remains in the mid stages of decomposition. 

Aims & objectives

1. Further characterisation of the crystals and bacteria

a. The bacteria are essential to the formation of the crystals and the proposed research aims to study them further to address questions relating to their identification and origin. Once bacterial samples have been collected and cultured from decomposing remains, a representative sample will be sent to the National Collection of Industrial, Food and Marine Bacteria (NCIMB) for genetic sequencing and identification. Furthermore, analysis of the chemical composition of the crystals using a variety of methods including Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX), and X-ray Diffraction (XRD) will occur.

2) Further investigation of the association between bacterial precipitation of crystals and the post-mortem interval

a. Further work will be conducted to correlate bacterial precipitation of crystals with time and its potential impact in determining the post-mortem interval. This will be carried out using a variety of microbiological and chemical techniques.                                                                   

Methods

Porcine trotters were obtained from a butcher and allowed to decompose in shallow burial conditions for various time intervals. Recovered samples were dissected and cartilage was extracted from the metatarsal joints. Porcine heads were also obtained and allowed to decompose in an outdoor, open air environment for various time periods. Cartilage samples were recovered by dissection from the: temporomandibular joint, snout, ear, and foramen magnum. Additionally, porcine eyes were also allowed to decompose under different temperatures in a laboratory environment. 

Bacteria from the cartilage and eye samples were collected via swabbing and cultured on a specialist medium (B-41) to allow for the formation of crystals. The bacterially produced crystals were analysed using chemical methods including X-Ray Diffraction (XRD) and Scanning Electron Microscopy with Energy Dispersive X-Ray Analysis (SEM-EDX).

DNA was extracted from cultured bacterial samples for DNA sequencing for the purposes of identification.

Summary findings

Post-mortem crystals were found to develop on porcine eyes, and cartilage collected from the trotters.

In burial environments, the crystals found on trotter cartilage form after 3 weeks and persist under 6 six weeks, after which they are absent.

Crystal producing bacteria were found in several anatomical locations including the trotters, eyes, and base of the skull. This suggests that the bacteria are systemic rather than localised, post-mortem. Further work is needed to explore this finding.

Bacteria cultured from eyes and cartilage produced crystals. Chemical analysis has tentatively identified these as struvite, but differences in the chemical compositions between the struvite crystals suggest that different species can form after death.

A bacterium from the trotters has been tentatively identified as Comamonas sp. The identification of the bacteria cultured from the porcine eyes is still on-going. Due to time constraints, identification of the bacterium by the NCIMB did not occur.

Acknowledgments:

Thank you to Dr. Michael Whitehead, Dr. Mark Morris, Professor Craig Williams, Antonia Dodsworth and Eleanor Baggs for assistance with data collection.

References

Haglund, W.D., Sorg, M.H.  (1997) Forensic Taphonomy, The Post-mortem Fate of Human Remains. Boca Raton, Florida: CRC Press.

Haglund, W.D., Sorg, M.H. (2002) Advances in Forensic Taphonomy, Method, Theory and Archaeological Perspectives. Boca Raton, Florida: CRC  Press.

Rogers, C.J., Clark, K., Hodson, B.J., Whitehead, M.P., Sutton, R., Schmerer, W.M. (2011) Post-mortem degradation of porcine articular cartilage. Journal of Forensic and Legal Medicine.18(2): 52 ‐ 56.

Rogers, C.J., ten Broek, C.M.A., Hodson, B.J, Whitehead, M.P., Schmerer, W.M., Sutton, R. (2014) Identification of crystals forming on porcine articular cartilage: A new method for the

Estimation of the post--‐mortem interval. Journal of Forensic Sciences. 59(6): 1575 ‐1582.

Vass, A. (2001) Beyond the grave-understanding human decomposition. Microbiology Today. 28, pages unknown.