Introduction
There are numerous descriptions of drowning that are available and actually, all of them bear some weight. According to Lunette, G., et.al death by drowning is the consequence of a obstruction of respiration by impediment of mouth and nose by a liquid medium which is more often than not water (2004). Actually, there are many other drowning definitions wherein all have some accuracy. In regards to true drowning, there are relatively no considerable disagreements, since there is a general conduit, which involves the water inhalation, which could eventually pass through the alveolo-capillary membrane thus eventually reaching the general circulation ultimately. Characteristically, a difference flanked by saltwater and fresh is made, even though this is fundamentally rooted in animal experimentations. Conversely, huge debates subsist concerning immersion death excluding true drowning, for example dry lung drowning and hydrocution. In addition, the pathogenic and physiological incidents are difficult to establish. Certainly, laryngospasm and vasovagal stimulation caused reflex cardiac arrest cannot be established throughout autopsy, however, favourising aspects for instance, cold-water and ethanol ingestion ought to be considered. In all actuality, immersion death excluding true drowning can never be validated via autopsy methods.
Such deaths can actually be of natural causes. According to Smith, G. M., et.al, to attribute drowning as grounds of death especially to a corpse discovered in water devoid of various confirmations of the consequence of containing absorbed water is uncertain. Therefore, in such circumstances, it could be more precise to indulge a differential diagnosis before an explicit cause of death (2005). Police information for example eye-witnessing can, as an example, is more dependable.
There are numerous methods of determining drowning however, for the sake of this paper, we will concentrate of the use of micro algae to determine death by drowning. As described above, drowning is a complex issue to deal with. Therefore, it is indispensable to employ correct techniques to establish death using microorganisms. In respect to this, a variety of microbes within the drowning water could be researched, for example diatoms and algae. Actually, Algae are the simplest structure of plant life. The word "alga,-ae" originates from the Latin phrase denoting seaweed, however, as employed currently includes numerous additional varieties. Whereas the enormous preponderance of algae is typically aquatic, a few species have adapted to growth in soil as well as in exotic environments like floating icebergs. They are mostly unicellular; however, some are multicellular, with immense cellular composition variations (Hayward et.al, 2004).
In comparison with the higher plants, algae have no exact stems, roots, seeds, or leaves. The essential metabolic process of nourishment and reproduction is entirely contained in the individual cell, exclusive of the land plants’ transport systems. The one characteristic general to all algae is photosynthesis, which is the light energy utilization in the conversion inorganic to organic materials. Algae have been comprehensively researched throughout the past six decades, and just over 17,500 species have been illustrated. Their categorization has been diverse, unstandardized, and in numerous examples moderately defectively confused. For numerous years, they were lumped into four primary collections rooted in gross coloration in the form of brown, red, green, and blue-green. With augmented comprehending of pigments, of metabolic reactions, and of reproductive mechanisms, algae are today classified into seven main Divisions.
Additionally, the term diatom factually denotes cut in to two. Diatoms are a category of algae. About 8000 species have been discovered and documented. They are unicellular living beings, which are found as both colonies and single cells. The key characteristic, which is employed to differentiate diatoms from other categories of algae, is the cell wall composition. The cell wall is silicified (Hayward et.al, 2004). Diatoms are extensively dispersed in both salt and fresh water. Definite diatoms species are merely established in fresh water while others are merely located in the salt water. In summary, diatoms are unicellular algae with chrysophyte-like photosynthetic tinctures. As mentioned earlier, the cell wall is silicified to appear like frustules, encompassing two valves, one vaguely bigger than other is and however, both fitting jointly similar to a box and lid (Hayward et.al, 2004).They are microfossils and have been documented and categorized for in excess of 200 years.
Categorization is principally rooted in the valve structure that is its outline, complicated prototyping, and decoration (Hayward et.al, 2004).
The generally recurrent forensic science application of diatoms is in the analysis of death by drowning. Drowning is a tremendously widespread fortuitous and suicidal basis of death, and thousands pass away per annum in this manner. The fundamental code of the diatom test in drowning is rooted in deduction that diatoms are available in the fluid where the probable drowning occurred and that the water inhalation caused the infiltration of diatoms into the alveolar scheme and into the bloodstream, and therefore, their deposition into other organs. The diatom analysis application in determining if drowning was the grounds for death has demonstrated to be a priceless instrument in forensic science. Pollanen (2007) backed the soundness and efficacy of the diatom analysis for drowning via the examinations of 771 drowning cases. In 90% of the cases wherein the drowning medium sample was obtainable, the bone marrow diatom corresponded with assemblages in the medium.
The diatoms recognition of in the body tissues to confirm a death by drowning recognized as the diatom test goes back to the conclusion of the 19th century. Conversely, in current decades the dependability of this technique was invalidated owing to an assumed imprecision and elevated false positive rate. However, the issue is still extremely contentious. Specifically, sample contamination throughout autopsy and contamination of tissue extracts throughout processing was acknowledged as the key grounds of false positive outcomes. Conversely, the likelihood of diatom inert infiltration into the body predominantly into lungs throughout submersion cannot be kept out, particularly in extremely distorted corpses. Therefore, tissues that are extremely isolated from the drowning fluid, for example bone marrow, are favoured as models, consistent with the most current literature. Extra drowning site information and situations can be obtained from the qualitative and quantitative assessment linking the diatoms established in the body tissues and those in the drowning fluid. From the investigative viewpoint, the mainstream authors of digest tissues by action with strong acids, habitually after oxidation; on the other hand, proteolytic enzymes are extensively employed. Recognition is usually achieved via light microscopy, but scanning electron microscopy (SEM) demonstrates much enhanced resolution, which is significant for the detection of the smallest diatoms or diatom portions.
Diatom Identification
The diatom test is yet to be a regular practice in latin America but has been widely used in countries like France and Japan. Diatom analysis involves using the following methods on tissues: Strong acid ,Tissue solubilizers and Enzymatic digestions. These methods are known to fail when used for marine diatoms, hence the need to develop different ways that can be used on different aquatic system.
Environmental conditions that affect the potency of Diatom Test
An experiment was done by Daiz-Palma PA, Alucema A, Hayashida G and Maidana NI of the Chemical and Pharmaceutical science departments, Universidad Catolica del Norte, Chile to develop and standardize Microalgae test for determining deaths by drowning. The following were done in the cause of the experiment: Different digestion techniques were compared to ascertain which provides the highest amount of microalgae using the bone marrow and water samples. Tissue samples (lung and sterna bone marrow) were obtained from 3 different drowned victims. Sea water samples close to where the victims were found was also collected. The best digestion method was chosen based on the one yielding the cleanest sample. It was noted that the enzymatic digestion treatment was more effective to remove the organic matter from human tissues than from the microalgae. When the enzymatic and chemical digestion was combined for use on tissue samples, it yielded better performance and increased the diversity of diatom, dinoflagellates and chlorophytes species. It was noted that chemical digestion was not favourable for seawater diatoms. Silica is scarcer in marine than fresh water environment (seawater diatoms contain less Silica than fresh water diatoms). Hence, combined digestion is used for sea water diatoms and Silico flagellates. It was noted that Dinoflagellate thecae was resistant to a combination of chemical and enzymatic treatment. (Daiz-Palma,T., 2004)
The combined digestion procedure when used increased the recovery of a larger number of evidence (Microalgae) in comparison with various methods. This technique preserves the algae material (protects cell covering) that easily becomes fractured when the other aggressive traditional techniques are used. Hence, a standardized microalgae test provides valuable evidence that can be used in court. However, diatoms and microalgae tests are not conclusive proof of death by drowning, they are only additional tools used with other forms of diagnosis such as Toxicological screening, complete autopsy, histological analysis of all organs, history of victims, eye witness presence etc on the basis of exclusion to ascertain the likely cause of death and reach a final decision.
References
Daiz-Palma,T., (2004) Development and standardization of microalgae test for determining deaths by drowning Universidad Catolica del Norte, Chile
Hayward BW, Scott GH, Grenfell HR, Carter R, Lipps JH (2004). Techniques for estimation of tidal elevation and confinement (salinity) histories of sheltered harbours and estuaries using benthic foraminifera: examples from New Zealand. Holocene;14:218–32.
Smith, G. M., et.al (2005) Manual of phycology; an introduction to algae and their biology, , Chronica Botannica Co., Waltham, Mass. 375.
Pollanen, M. S. (2007). “The diagnostic value of the diatom test for drowning, II. Validity: analysis of diatoms in bone marrow and drowning medium”. Journal of Forensic Sciences, 42(2), 286-290. Retrieved from http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=9068188
Lunette, G., et.al, (2004) Undetermined drowning, Med. Sci. Law 43 207–214.
Karkola, H., and Neittaanma¨ki, S., (2006) Diagnosis of drowning by investigation of left heart blood, Forensic Sci. Int. 18 149–153.
