Scientists look for correlation between the time bones are submerged in sea water and the amount of substitutions of bone mineral Hydroxyapatite. Credit: Dreamstime
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In forensic investigations unearthing the post-mortem interval (PMI) or time since death is crucial for identifying the remains and reconstructing the events that occurred at or near the time of death. When a body is discovered, pathological evaluations are largely hindered by post mortem changes and often a combination of factors such as temperature, surrounding environment and activity of insects need to be studied in order to ascertain the most accurate probable PMI. However whilst various techniques for analysing the PMI of bodies found on land are well researched, the literature covering topics concerning decomposition and forensic science in aquatic and marine environments is scarce. Could neutrons detect the missing clues? Well, a group of scientists, Dr S Vanin, Professor R Cywinski, and Professor S H Kilcoyne, from the University of Huddersfield and Dr Stewart Parker, ISIS instrument scientist, have been using ISIS to find out.
Scientists embark on a preliminary study on the TOSCA instrument at ISIS in the attempt to establish and validate a method to estimate the time of bone submersion in sea water.
Forensic recoveries from bodies of water are quite common; each year hundreds of migrants die or are reported missing whilst travelling to their destinations. In 2011 the UN refugee agency reported that “Based on telephone calls from boats in distress and reports from survivors and family members” 1,500 individuals attempting to migrate from Libya to Europe died en route. However, identifying many of these missing people who die at sea is difficult, as the decomposition of human remains underwater involves both complex and highly variable processes, meaning reliable dating of skeletonized remains presents a scientific challenge. Furthermore, studies documenting human remains recovered from water are few and far between.
Dr Stefano Vanin, University of Huddersfield, explains “When a cadaver reaches an advanced stage of decomposition, in particular when only skeletal vestiges are recovered, estimation of the PMI is increasingly problematic. As a forensic entomologist, I have studied insects that develop on decomposed bodies as a way of estimating the time of death. However when faced with cases of drowning, just by studying the insects we don’t get many clues with regard to the time of submersion. It’s astonishing the number of people that die travelling from Africa to Europe and in absence of other evidence the estimation of time of submersion of a skeleton can be of fundamental importance in order to identify the victims.”
Stefano believes neutrons provide the solution.
“When you find a skeleton it doesn’t always mean it’s a forensic case – it could have died sixty or seventy years ago or it might be an archaeological case. If it is a forensic case, we want to understand the year which the crime happened or the death happened and at the moment we don’t have an instrument to detect or at least try to detect this at this time.”
“So with this in mind an idea started flickering in my head - we have a bone, from a chemical point of view it’s a stone but at the same time it’s like a sponge so I can expect a substitution of different things from the sea water and what is fantastic is with the neutron scattering we can detect a substitution of atoms. So this was my idea, if we can find a correlation between the time bones are submerged in sea water and the amount of substitutions we can come up with a scale that we can use to calculate the time of submersion for post mortem analysis.”
The crystal structure of Hydroxyapatite. Credit: Anna Tanczos, Wellcome Library, London. Image on the right shows a CT reconstruction of one of the bones the team analysed using neutrons.
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Bones are made up of very few cells called osteoblasts which deposit Type-1 collagen to form a surrounding matrix. The cells also release calcium, phosphate and magnesium ions which combine with the matrix to form the bone mineral. This is called hydroxyapatite (HA) and is a crystalline mineral. HA can undergo chemical substitutions with foreign ions and these reactions result the alteration of the bone property– and it’s these substitutions that the team want to detect.
In order to do this the team submerged pig bones in sea water for varying amounts of time. They then used neutrons to detect compare the substitutions that had occurred in each of the samples.
“We are working with two different samples; one submerged for a week and another one immersed in the sea water for four months. We are using inelastic neutron scattering on TOSCA to see if we can detect a difference between the two samples and in a certain way quantify this difference. We will combine the results with Raman scattering and infrared measurements.”
“The idea is to make a sort of temporal scale for which after these experiments we will have two points. If however we are able to detect this difference we will study another point and one or to external points to build up the scale. We are also testing with two controls, a bone in fresh water and a bone in dry conditions and we are also looking at bones submerged in sea water ten times the concentration to see if the substitution reactions depend on the concentration.”
Early results are looking promising and the team plan to return to ISIS to continue their experiments in the near future.
Research date: March 2014
For more information please contact Dr S Vanin
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