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The effect of different detergents on the removal of bloodstained clothing
Blood is considered to be class evidence in the world of criminal justice.' There is no substitute for it, whether it is for medical purposes or forensic purposes. Its presence never fails to link suspect and victim to one another and the scene of violence'4. Bloodstain patterns have the ability to provide vital information in order to unfold crime scenes, the position and movement during the attack, who struck whom first, in what manner and the number of times. In the law of courts this information destroys the most alibi and self-defence arguments of crime and can trip up most suspects in their explanation of what occurred.
'The blood carries a volume of around five litres and a weight of 5.5kg in an average person'5. Normal Peripheral blood is composed of three types of cells; red cells (erythrocytes), white cells (leucocytes) and platelets (thrombocytes), all of which are suspended in a pale yellow liquid known as plasma. 'Blood is a slightly alkaline fluid which composes of 55%, 45% is solid which is made up of water, cells, enzymes, proteins and inorganic substances'4 all of which circulate throughout the body, supporting the function of all other bodily tissues. 'When analysing blood stains forensic scientists are more interested in the red cells and serum. As serum has the potential to form several minutes after exposure to air, it gives analyst the ability to establish the freshness of a blood sample.'4
Criminals have deliberately tried many ingenious ways to conceal or remove blood stained evidence that has been transferred to garments during a violent act, by washing their clothes. Cleaning agents, such as detergents not only have the potential to remove blood but can also contaminate and degrade DNA which could be used in evidence in the court of law against justice.
Dr Otto Rohm established a concept in 1913, in which enzymes were used in detergents. He patented the use of crude pancreatic extracts in laundry pre-soak compositions in order to improve the removal of biological stains.
Enzymes facilitate the removal of diverse stains which would otherwise be complicated to eliminate with detergents. Being catalysts they have the ability to be fully effective in low concentrations. Those enzymes used in detergents are protein catalysts that consist of long amino acid chains. Being similar to protein catalysts in all living cells they can control metabolic processes and break down larger substrates into smaller substrates. Certain molecules found in stains can latch onto the active site of an enzyme forming an enzyme substrate complex; this is where the enzyme breaks the molecule into smaller more manageable sections that are easy to dissolve in the detergents. Such enzymes which are used in laundry detergents work best in temperatures ranging from 20-60oC.
Proteases, amylases, lipases and cellulases are the activate enzyme ingredients in most laundry detergents to date. However some miscellaneous enzymes are also involved, these being peroxidises' and pullulanase.
Within the action of proteases, large protein molecules are hydrolyzed. The action of hydrolysis within this enzyme breaks down the peptide bonds that hold a number of amino acids together creating large protein molecules; this process releases smaller soluble polypeptides and individual amino acid units. Proteases are predominantly used in the removal of protein stains, for example blood and human sweat, organic stains as such have the tendency to strongly adhere to textile fabrics. The combined effect of surfactants and enzymes allows the removal of these stubborn stains from clothing fibres.
Amylase facilitates the removal of starch-based stains; this is through the breakdown of the stains from larger starch molecules into smaller segments which make up the stain, the enzyme catalyses the hydrolysis of glycosidic linkages in starch polymers. The products released from the enzymes hydrolytic action are oligosaccharides and dextrins, these products being soluble. This solubility allow the stains to physically break free from the surface of the material being washed, the enzyme acts as scissors within this process gradually removing the stain.
Lipases is an enzyme used to breakdown fats, this occurs through the hydrolysis of water insoluble triglycerides components into more water soluble products as monoglycerides, diglycerides, single fatty acids and glycerol.
The performance of cellulases within laundry detergents are mainly for their whitening elements. This enzyme removes micro fibrils from cotton based fabrics.
The first miscellaneous enzyme is Peroxidise a haem containing protein, which in the presence of water uses hydrogen peroxide as the electron acceptor to catalyse a number of oxidative reactions. Pullulanase is the second miscellaneous enzyme; this enzyme is used in combination with other amylolytic enzymes in detergents for improved stain removal and enhanced cleaning performance.
Non-enzymatic detergents are inefficient in the removal of proteins; this inefficiency can result in permanent stains, this occurs through the oxidation and denaturing by bleaching and drying. Blood for example will leave a rust coloured spot unless it is effectively removed by the action of specific proteins, mainly proteases, or before bleaching and washing.
Blood stain removal can be one of the most difficult cleaning processes, and depending on the surface and type of material stained, there are a number of different detergents that can be used in the aid of this elimination. In cases where blood is not effectively removed this gives forensic scientists the opportunity to detect the DNA of the blood. There are two main blood tests which are used by forensics to detect the presence of blood and in relation to DNA blood analysis; the Kastle-Meyer (KM) test and the leucomalachite green presumptive (LMG) test.
The Kastle-Meyer test is a presumptive blood test employed by forensics in the chemical identification of blood. The KM test uses a clear chemical indicator known as phenolphthalein in order to detect the possible presence of haemoglobin. In the presence of haemoglobin the chemical indicator immediately turns pink after oxidisation with the both haemoglobin and hydrogen peroxide.
The second presumptive blood test carried out in crime labs by forensic scientists is the Leucomalachite Green blood test. This is a catalytic test which also like the KM test, is based on the peroxidise-like activity of haemoglobin. The Haemoglobin molecules in blood have the ability to cleave oxygen molecules from water (H2O2) and catalyze the reaction from the reduced form of leucomalachite green to the oxidised blue-green colour instantly which signifies the presence of blood.
A study similar to this project has been carried out previously but with the intention of different aims, the study of Harris, K., Thacker, C., Ballard, D., and Syndercombe, D., Court (2006), aimed to test 'the effect of cleaning agents on the DNA analysis of blood stains deposited on different substrates'. The findings from this study demonstrated that the chlorinated bleach had the most deleterious effect on the quality of the DNA profile from the blood samples.
Chlorine bleach and oxygen bleach are the two forms of bleach which are found amongst cleaning products.
Chlorine bleaches has the strength to remove aÂ bloodstain to the naked eye and eliminate traces of blood. However in some cases there may still be minute traces of blood even though it appears otherwise when visualised. With the aid of substances such as luminol and phenolphthalein used within chemical blood tests, expert forensics have the ability to identify the presence of blood through the oxidation of haemoglobin molecules. Even if the criminal washed a bloodstained item of clothing several times with chlorine bleaches, these chemicals could still reveal blood.
Oxygen bleach is a chemical solution which contains an oxidising agent, for example hydrogen peroxide. In this case, when washing the bloodstained item of clothing with oxygen bleach haemoglobin is completely removed and cannot be detected further if presumptive blood tests are undertaken. This creates a huge challenge within the court of law against criminals as it can significantly compromise an investigation as it may mean that valuable evidence is not efficiently investigated.
A recent study in relation to this project was conducted in 2008 by Sarah M. Don; the author researched 'the effects of chemical constituents of laundry detergents and methods of stain removal'. The aim of this investigation was to identify the effectiveness of certain laundry detergents and stain removal methods by comparing their constituents' chemical properties.
Baring in mind the findings of Harris, K., Thacker, C., Ballard, D., and Syndercombe, D., Court (2006), and Sarah M. Don (2008), the purpose of this project will be to gain a better understanding on 'the effect of different detergents on the removal of bloodstained clothing', therefore establishing which detergents are best used to conceal and remove bloodstained material by vicious criminals. Furthermore conducting this investigation will allow me to determine if there is the ability to extract DNA from the garments once washed through with these detergents, in order to identify the criminals and victims of crime.