Presumptive Tests that are Used for the Analysis of Blood or Bloody Fingerprints at a Crime Scene - Article Example

Presumptive tests that are used for the analysis of blood or bloody fingerprints at a crime scene Student name: Student number : Institution name: Course id : Tutor: Submission Date: Blood is the most common and the most important form of evidence in the world of criminal justice today (Cox 2004). Blood found at the crime scene can provide important information that may help solve a case, backup testimony of the witness, link a suspect to a crime and define the scene of crime or it may also offer a new direction in the investigation. It is essential to clearly define blood stains at the crime scene to help in investigation (Schiro 2004). The advantage of blood stains at the crime scene compared to others is that it cannot be identified using reagents to quickly identify it. The question that an investigator should be able to answer in a crime scene once they find blood is why the presence of blood at the crime scene. Proper methods should be used to test the blood in order to offer credible evidence. According to Cox (1991) describes the attributes that of a good presumptive test for blood should have; it should be sensitive, specific, quick, simple and safe. The other questions that are raised from a blood sample at a crime scene are the person to whom the blood belongs. There should be enough blood samples to have a comprehensive DNA profile. A component of blood in a given sample is required for presumptive tests of blood to function. A component of blood is critical since it is not found in everyday environment hence unique. Presumptive tests are based on peroxidise-like activity of haemoglobin (Cox 2004). Given that blood that has a connection with a crime scene can be used to solve the by giving important information, it must be collected and documented. Blood is nowadays being accepted in the court of law as evidence and it can be based on in making major ruling. There must be a proper way of handling blood as evidence in order to ensure that evidence is not weakened or destroyed (Cox 2004). There have been many studies that have investigated presumptive tests based on its sensitive and specificity and its impact on DNA analysis. Presumptive tests can establish the possibility that a specific bodily tissue or fluid is present. Confirmatory tests are used to conclusively identify the identity of a controlled substance. This process may comprise one of the technical procedures or a mixture of two or more technical procedures. The first step in a crime scene is to ensure that it is secured and clearly marked. Documentation of the scene is clearly done to ensure that everything that is in the scene can be used as evidence to solve the case (Comey and Budowle 1991). To ensure that evidence is not destroyed or compromised it should be quickly documented collected and preserved. Collection of evidence at the crime scene always begins with evidence that is fragile and easily lost. To avoid contamination blood collected from the scene should be well packaged and safely kept (Comey and Budowle 1991). it is also worth noting that evidence that contain moisture should not be packed in plastic that are sealed or paper containers since moisture enables growth of microorganisms that can change or destroy evidence. According to Fisher and others (1981), bloodstains that are dried up can be collected and packed in a paper bag or an envelope. It is easy to transport such content for testing in the lab. However, such samples means that the serologist has to do more work of extracting the blood sample. Some cases blood sample can be very large, this means that it cannot be transported. There are other methods that can be used in collecting samples of large blood stain item. The first method is to cut out the parts of the item that has bloodstains. To ensure that tests are reliable a control part one without blood stain from the same item is also extracted. Tape lifting bloodstains is another method of taking blood samples from a not transferrable item. Fingerprints tape can be use to rub the bloodstain surface in order to lift bloodstain on the tape. Although this method minimises many contamination such as water, tapes sometimes may not collect bloodstains in other surfaces very well (Lee 1982). Bloodstains can be collected from the item by scrapping it off the surface. This method should not use a plastic container is storing the evidence instead use a paper packet. There are other methods that investigators can use to extract bloodstains from a surface especially if the sample is dry. Investigators choose a given method of extracting based on the nature of the surface in which blood stains are on. Investigators can also encounter wet bloodstains. This is a case where the investigators arrive at the scene few hours after the incident. There are methods used to test blood samples. They include; Phenolphthalein test also referred to as Kastler Meyer Test, Luminol Test referred to as Albrecht reaction and alternate Light Source (Comey and Budowle 1991). Kastler Meyer Test is a forensic presumptive blood test. This method uses the chemical called phenolphthalein which is a clear dye, the observations are that it turns pink if oxidized by haemoglobin and hydrogen peroxide. In this test heme molecules acts as a catalyst and it is based on peroxide-mediated oxidation of reduced phenolphthalein. Cotton swab are used to collect blood stains for testing. This test does not destroy the sample hence the sample can be kept for future use. The test gives positive results or same results for both animals and human hence further testing is required to determine which one does the sample belong. The reagents that are used in the experiment include: Phenolphthalein this is a solution which acts as a colour indicators. The solution is boiled several hours to get rid of the oxygen dissolved in it. The solution should appear as a colourless liquid. Hydrogen peroxide: this is a solution of water with extra atom of oxygen attached to it. Alcohol: Methyl alcohol is used to increase the sensitivity of the test. It is used to clean up the area around and in the bloodstain to better expose the haemoglobin. The procedure There are about seven steps that should be followed in carrying out this test. The safety measure is that one should put on safety goggles and gloves that are disposable. Obtain cotton swab. The next step is to apply one drop of ethanol from the dropper bottle to the swab while holding the swab over the plastic waste dish. Rub the surface of letter opener suspected of blood with swab 4- 5 minutes. Apply one drop of phenolphthalein solution from the dropper bottle to the swab while holding the swab over the plastic waste dish. Then apply one drop of hydrogen peroxide solution to the swab immediately. The sample is positive for blood if the colour changes to pink within 10 seconds. The sample of negative of blood if the swab does not change to pink within 10 seconds. The nail file can be used instead of letter opener in determining blood sample (Comey and Budowle 1991). This is presumptive test of blood especially when no bloodstain is found at the scene of crime, then it is used to test for blood. Luminol test has a high sensitivity compared to other forensic tools of blood test. Walter Sprech first described luminol test for blood in 1937 and it has been widely used in forensic field since then (Quickenden and Copper 2001) Luminol test is used all over the world because of its great sensitivity in crime scene. Blood is one of the most common physical evidence found at a violent crime scenes. The blood once analysed by forensic experts offer essential explanation about the crime. Luminol tests are used to answer questions such as if the stain is really blood and if so is it human blood? Further questions about sex and identity of the blood sample are also addressed. There is a difference in colour and composition of fresh bloodstains and aged bloodstains. Fresh bloodstains have a feature of red colour through the erythrocytes, but when they stains age they turn into a brown colour through alterations of the haemoglobin (Patzelt 2004). It can be difficult to see stains in some surfaces and even hard to separate the stains from the said item. Previously other forensic blood tests were done before the discovery of presumptive tests (James, Kish, and Sutton 2005). However, these tests they produce negative and positive results that are false to some degree hence they are only presumptive (James, Kish, and Sutton 2005). Leucomalachite green (LMG) is commonly used as a presumptive test. The most important aspect of forensic analysis of blood is to identify who shed the blood. Linking the bloodstains to the real person who shed it has been a challenge for many years, techniques such as ABO-systems and characterization of serum proteins have been used for such exercises (Patzelt 2004). DNA-techniques has replaced most of the early techniques used to test identity of the blood sample. Currently PCR and typing of short tandem repeats (STR) markers are being used in forensic blood tests in many laboratories. Sex determination is now possible due to this methods the DNA-techniques (Patzelt 2004). Many compounds apart from haemoglobin give rise to CL of luminol in different reactions. Therefore, the chemistry behind CL of luminol is important in many biochemistry fields. According to (Baj and Krawczyk 2006; Creamer et al. 2003), there are many complex reactions that lead to CL of luminol with the probability that some are even not yet documented. Although the precise mechanism is not yet known in blood test, haemoglobin are the elements in bloodstains that facilitate the reactions that lead to CL. Luminol is implicated in the forensic test of blood by an alkali solution ant the presence of an oxidant. Oxidation of luminol is enabled by the alkali condition and catalytic activity of haemoglobin with the help of the catalyst (Baj & Krawczyk 2006). This process has three important steps referred to as 3-aminophthalat from which oxidation transcend up to the intermediate step where light is radiated (Marquette and Blum 2006). A schematic representation of the reactions between luminol and hydrogen peroxide which is an oxidant is catalysed by horseradish peroxidase (HRP) in an alkali solution. The enzyme initiates reaction of oxidation by hydrogen peroxides in step I and II. Preparation process for this test has been described by many with an aim of maximizing forensic analysis outcome. Grodsky et al. (1951) and Weber (1966) describes the process of luminol tests each giving advantages and disadvantages of their preparations (James, Kish and Sutton 2005).the reactions in the forensic preparations where luminol produce CL can be initiated by different compounds. Interference to the luminol test for blood is high due to the fact that the test is very sensitive to blood. If the test is limited of its blood sensitivity then it becomes a disadvantage. There are several factors that can lead to luminol test being lest sensitive to blood. The effect of bloodstain preheating and older stains- When bloodstains dry up and stay for longer period, there are different processes that take both chemical and biological. Haemoglobin changes to methemoglobin as a result of these changes when iron in the heme prosthetic groups oxidize from Fe(II and III) (Patzelt 2004). The catalytic properties of blood is destroyed hence when luminol tests are done there is no reaction to produce lumionl CL. It is possible to carry out luminol tests repeatedly but there is no quantitative instigation that has been done is such manner (Baj & Krawczyk 2006). Preheating is another factor that affects luminol tests. Quickenden et al (2001) describes the impact of preheating on the blood tests. In the experiments, it was observed that CL measures increases with an increase in temperature. This shows how blood in a motor vehicle expose to different temperatures can show different results. Quickenden et al (2001), further illustrates how these changes results into the formation of methemoglobin from haemoglobin generated by heat as illustrated below. Heat results into a reaction that alters the charge of iron from iron II (Fe++) to iron III (Fe+++) hence change from haemoglobin to methaemoglobin. Mimicking interference of the luminol tests for blood- Walter Sprecht in 1937 in the description of the forensic use of luminol test stated that there are other elements apart from blood that give CL in the solution applied (James, Kish and Sutton 2005). It was further established that apart from peroxidises other haemenzyms such as iron and copper, sodium hypochlorite of bleachers also give CL (Quickenden and Creamer 2001). The early studies did not provide substrate and compounds that mimic positive tests. Attempted cleaning of bloodstains -Since hypochlorite give strong CL and it is also used to bleach it can be used to clean bloodstains from scene of crime. This has resulted into intensive study of the effect of hypochlorite on luminol test (Baj & Krawczyk 2006). When water is used to clean bloodstains, the measured CL decreases until negligible with several washes but when hypochlorite is used to wash away bloodstains, the CL decreases initially but later it increases until it reaches stabilized value comparable to the bleach gave a CL (Quickenden and Creamer 2001). This is a crime scene technique used by investigators and lab technicians for enhancing observation, photography in the process of collecting evidence from the crime scene which includes drug traces, body fluids fingerprints among forensic evidence. It is used to increase the amount of evidence collected from a crime scene with high quality. Body fluid can be detected using this type of light source since body fluids such as semen, saliva, blood and virginal fluids are fluorescent by nature (Quickenden and Creamer 2001). Using source light forensic investigators can narrow down into a specific location instead of searching the entire area. Dried body fluids glow under the light source illumination. References Baj, S and Krawczyk, T, 2006, An investigation into the reaction of hemin-catalysed luminol oxidation by peroxy compounds. J Photochem Photobiol A: Chemistry, doi:10.1016/j.jphotochem. 2006.03.002 Creamer, JI, Quickenden, TI, Apanah, MV, Kerr, KA and Robertson, PA 2003, A comprehensive experimental study of industrial, domestic and environmental interferences with the forensic luminol test for blood. Luminescence 2003 18:193 – 198 Comey, CT, and Budowle, B 1991, Validation Studies on the Analysis of the HLA DQà Locus Using the Polymerase Chain Reaction, Journal of Forensic Sciences, Vol. 36, No. 6, Nov. pp. 1633-1648 Cox, M 1991,A study of the sensitivity and specificity of four presumptive tests for blood. J Forensic Sci.;36(5):1503 – 11 Fisher, Barry AJ, Arne Svensson, and Otto Wendel (1981), Techniques of Crime Scene Investigation. New York: Elseveir. Grispino, RRJ 1990, The Effects of Luminol on the Serological Analysis of Dried Bloodstains. Crime Laboratory Digest, Vol. 17, No. 1, Jan, pp. 13-23. James, SH, Kish, PE and Sutton, TP 2005, Principle of bloodstain pattern analysis: theory and practice, CRC press Taylor & Francis Group, ISBN 978-1-8493-2014-9 Lee, HC 1982, Identification and Grouping of Bloodstains, in Forensic Science Handbook, Saferstein, R., ed., Prentice-Hall, Inc., Englewood Cliffs, NJ. Quickenden, TI and Copper, PD 2001 Increasing the specificity of the forensic luminol test for blood. Luminescence, 2001 16:251 – 253 Marquette, CA and Blum, LJ 2006, Applications of the luminol chemiluminescent reaction in analytical chemistry. Anal Bioanal Chem, 385(3):546 - 54. Quickenden, TI and Creamer JI 2001 A study of common interferences with the forensic luminol test for blood. Luminescence, 16:295 – 298 Quickenden, T. I., Ennis, C.P. and Creamer, J.I., The forensic use of luminol chemiluminescence to detect traces of blood inside motor vehicles. Luminescence, 2001 19: 271 – 277 Schiro, G 1995, Collection and Preservation of Evidence. What We Do - Law Enforcement Series. Compiled by Captain Merril L. Boling, Jefferson Parish Sheriff's Office. Webb, JL, Creamer, JI and Quickenden, T. I 2006, A comparison of the presumptive luminol test for blood with four non-chemiluminescent forensic techniques. Luminescence, 2006 10.1002/bio.908 (epub ahead of print) Read More

According to Fisher and others (1981), bloodstains that are dried up can be collected and packed in a paper bag or an envelope. It is easy to transport such content for testing in the lab. However, such samples means that the serologist has to do more work of extracting the blood sample. Some cases blood sample can be very large, this means that it cannot be transported. There are other methods that can be used in collecting samples of large blood stain item. The first method is to cut out the parts of the item that has bloodstains.

To ensure that tests are reliable a control part one without blood stain from the same item is also extracted. Tape lifting bloodstains is another method of taking blood samples from a not transferrable item. Fingerprints tape can be use to rub the bloodstain surface in order to lift bloodstain on the tape. Although this method minimises many contamination such as water, tapes sometimes may not collect bloodstains in other surfaces very well (Lee 1982). Bloodstains can be collected from the item by scrapping it off the surface.

This method should not use a plastic container is storing the evidence instead use a paper packet. There are other methods that investigators can use to extract bloodstains from a surface especially if the sample is dry. Investigators choose a given method of extracting based on the nature of the surface in which blood stains are on. Investigators can also encounter wet bloodstains. This is a case where the investigators arrive at the scene few hours after the incident. There are methods used to test blood samples.

They include; Phenolphthalein test also referred to as Kastler Meyer Test, Luminol Test referred to as Albrecht reaction and alternate Light Source (Comey and Budowle 1991). Kastler Meyer Test is a forensic presumptive blood test. This method uses the chemical called phenolphthalein which is a clear dye, the observations are that it turns pink if oxidized by haemoglobin and hydrogen peroxide. In this test heme molecules acts as a catalyst and it is based on peroxide-mediated oxidation of reduced phenolphthalein.

Cotton swab are used to collect blood stains for testing. This test does not destroy the sample hence the sample can be kept for future use. The test gives positive results or same results for both animals and human hence further testing is required to determine which one does the sample belong. The reagents that are used in the experiment include: Phenolphthalein this is a solution which acts as a colour indicators. The solution is boiled several hours to get rid of the oxygen dissolved in it.

The solution should appear as a colourless liquid. Hydrogen peroxide: this is a solution of water with extra atom of oxygen attached to it. Alcohol: Methyl alcohol is used to increase the sensitivity of the test. It is used to clean up the area around and in the bloodstain to better expose the haemoglobin. The procedure There are about seven steps that should be followed in carrying out this test. The safety measure is that one should put on safety goggles and gloves that are disposable.

Obtain cotton swab. The next step is to apply one drop of ethanol from the dropper bottle to the swab while holding the swab over the plastic waste dish. Rub the surface of letter opener suspected of blood with swab 4- 5 minutes. Apply one drop of phenolphthalein solution from the dropper bottle to the swab while holding the swab over the plastic waste dish. Then apply one drop of hydrogen peroxide solution to the swab immediately. The sample is positive for blood if the colour changes to pink within 10 seconds.

The sample of negative of blood if the swab does not change to pink within 10 seconds. The nail file can be used instead of letter opener in determining blood sample (Comey and Budowle 1991). This is presumptive test of blood especially when no bloodstain is found at the scene of crime, then it is used to test for blood. Luminol test has a high sensitivity compared to other forensic tools of blood test.

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