From deserted fields and dark woodlands to murky rivers and concrete jungles, environments can leave traces of physical evidence on a criminal. This principle has been well known to crime scene researchers( both real and fictional) since the the late 1800 s. However, figuring out what the most reliable pieces of evidence are and how to best detect and analyse them can be difficult.
Microscopic algae, such as diatoms, can be picked up from virtually anywhere there is water including oceans, ponds, soils, some domestic water supplies and even moist surfaces such as uncovered boulders. While diatoms traditionally have been used to diagnose demise by drowning, research is unravelling their huge potential for use as tracing proof in a range of forensic investigations.
Diatoms seem golden brown to the naked eye. However, when ensure under the microscope, they display a beautiful scope of shapes, colours and ornamentation. There are estimated to be more than 20,000 species worldwide. Diatoms are composed of silica recently determined to be the strongest natural material on the planet.
Although most forensic investigations are carried out on dry land, roughly 71% of the Earths surface is covered in some sort of water. Such marine or freshwater surroundings are often encountered as crime scene locatings or sites of accidental demise, suicide and natural or civil disasters( including airliner accidents ). Even when international crimes is carried out on land, water scenes may be used by a perpetrator to dispose of any incriminating evidence.
Diatoms through the microscope Prof. Gordon T. Taylor, Stony Brook University/ wikimedia
Diatoms are useful when diagnosing drowning as a cause of death. Their microscopic sizing and presence in standing and flowing water means they are often inhaled and swallowed during drowning. They are then transported throughout the circulatory system, and deposited in various organs including the lung, brain and bone marrow.
Diatoms can be observed under a microscope after a post-mortem examination. They can then be compared to the diatoms in the water where the body was observed. If diatoms are not present in the body, it may mean that the main victims didnt succumb by drowning after all. If the diatoms in the organs are significantly different from those in the water in which the body was discovered, it may mean that the main victims has been intentionally drowned elsewhere and then endeavoured to a second location in order to make a crime appear accidental.
Although widely used, the accuracy of the diatom exam for drowning is highly debated among experts. It is generally agreed that diatom analysis can provide important evidence of drowning, but should be used alongside other independent techniques within forensic pathology.
Research has also demonstrated how diatoms can be used to estimate the time since demise a crucial piece of information in any forensic investigation. This is notoriously difficult to do in water, with scientists often drawing conclusions based on the bodys level of decomposition and the presence of insects and bacteria.
In one analyse, scientists examined the accumulation of algae over day on animal remains as a proxy for humans. The diversity of algae on piglet bodies in water tended to decrease over hour with a peak in diatoms recorded after 1-8 days of decomposition. This various kinds of run remained largely experimental, but it has potential to be used for establishing a timeline since demise( or submersion) in water.
Every contact leaves a tracing
Diatoms are also depicting promise as trace proof indicators. The notion that offenders often unknowingly pick up tracings from a crime scene while leaving their own behind, has already led to the forensic examinations of materials including dust, paint fragments, hair, fibers, clays, bacteria and pollen.
The reason diatoms are so useful in this regard is that they are so abundant in so many different environments. Microscopic assessment of diatoms found on dres, footwear and personal belongings have already provided evidence in cases including homicide, serious assault, and serial burglary across Europe and the US.
For example, in 1996, a female victim was recovered from the Hudson River, in the US. A post-mortem revealed that she had been medication and strangled, before being drowned in the river. Diatoms recovered from the victims bone marrow were different from the water supply at her home but could not be ruled out from the scene of the crime. During the investigation, diatoms collected from the suspects wallet and shoes a link to the drowning site, helping to solve the case.
However, despite this initial success in case work, there are relatively few forensic diatom experts worldwide. As a outcome, diatoms are less frequently analyse as trace evidence than pollen and soils, for example. To fully realise their potential in forensic science, more research will be needed.
It is important to know how to collect any adhered diatom proof from garb, for example. Research has investigated the exact mechanisms by which diatoms stick to cotton dres in both water and soil and how to get them off so that they can be used as evidence. The outcomes highlighted that treating garment with hydrogen peroxide was effective. If the diatoms are not isolated in this way, other biological material on the cloth such as other algae or pollen can make it hard to properly identify them under a microscope.
The field of diatom analysis in forensic science is very much emerging and has considerable potential for further research and application in case work. The stakes are high. Aquatic systems are complex and notoriously difficult for forensic scientists to analyse, so using diatoms as a reliable tool would have a huge impact for crime scene investigation.
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