The Value of Blood Testing and Analysis - Research Paper Example

The Value of Blood Testing and Analysis: Understanding the Blood Analysis Forensic Process at a Crime Scene And in Measuring Drunk Driving Alcohol Levels Introduction This paper is an analytical research paper on what occurs at the crime scene in terms of collecting blood samples and what blood testing processes occur while collecting the samples. Whenever the police and investigators are called to a crime scene where injuries and/or death have occurred and blood splatter is involved, the forensic team is called in to collect samples to determine where, and from whom, the blood came from. Most of the time, blood splatter will belong to the victim, but there may be other spots of blood which could come, either from the victim, or from the perpetrator, or even a third party, like the family dog. All blood splatters and other similar evidence must be collected for further analysis to get a better picture of what happened at the scene and, more importantly, who was involved (NFSTC 2). In the second part, blood can also be analyzed for levels of alcohol in order to determine if a driver is driving over the alcohol limit, and must be taken to the police station and jail. Crime Scene Blood Analysis Blood contains plasma and serum in liquid format and also red and white blood cells, platelets and proteins. While blood is a liquid inside the body, once it leaves through a wound or some other process, the blood, once expended, will clot and dry out. There are three types of bloodstains categorized in forensics: passive stains which are created by drops of blood, blood flow and blood pooling; transfer stains whereby an object, such as someone’s shoe, a hand print or smearing from moving something through blood; and the impact stain which comes directly from spattering, blood swipes and splashes, usually from an implement used to cause the impact (NFSTC 3). Within these categories of blood evidence, there is also types of spatter, for example, the gunshot spatter, a cast-off spatter from swinging an object with blood on it, arterial spray which occurs when an artery is severed, expirated spatter which is blood expelled from the lungs through the nose or mouth and is more of a mist (NFSTC 6). There are many more types of bloodshed events, all of which create patterns. Within those patterns are voids, where an object may have blocked part of the spatter. This is also important in determining if something is missing from the crime scene as, if the object is found, the same spatter pattern will also be there. This is not only determined from the pattern but from analysis of the blood composition (NFSTC 7). Crime Scene Blood Splatter (Fig. 1, NFSTC 2) In the new age of DNA analysis, blood is even more so able to provide its own story about what occurred, who did it, and when event was done. Meticulous evidence notation is made for each blood sample taken and, along with photographic evidence that supports the blood taken from that position at the crime scene, much can be learned which can be evidence against a suspect in a jury trial (NFSTC 8). In some crime scenes, bloodstains can overlapped, creating a more challenging situation in determining details. Preliminary scientific analysis can be conducted at the crime scene while collecting the blood sample and there is a very careful process of making the collection, completing documentation of the evidence, and performing the preliminary analysis onsite. Such tests are conducted by professional blood analysts but the more in-depth analysis must always take place in the laboratory for better accuracy. The latest news in blood forensics is that there is now a test that can be done onsite at the crime scene to determine the gender of a suspect (Muirhead web). Within a colorimetric assay, enzyme biomarkers of creatine kinase (CK) and lactate dehydrogenase (LDH), which was first developed to determine ethnicity, another biomarker, alanine transaminase (ALT), is now combined to determine male or female serum blood samples. In the final step of conducting that analysis, the distinguishing feature is amplified, using a colored compound that provides the visual test result (Muirhead web). While it is not always absolute, it does give police officers at the scene something to work with, particularly if they have suspects in custody. In some crime scenes, evidence may had been cleaned up by the suspect and therefore, it is important to use a blood sample as a positive control when checking areas around the crime scene, such as in another part of a house where a murder took place. There are special sprays which can be sprayed around on surfaces that, when the lights are lowered, or shut off, will highlight blood that may have been cleaned away when a flashlight is shown on the surface. Chemicals, known as peroxidase reagents, will not react with fluids (other than blood), but will show blood, urine, and other body fluids will be detected. Invisible Blood Splatter Highlighted with Florescent - Luminol Fig. 2, NFSTC6) While hydrogen peroxide (H2O2) is one compound used, which does react to blood, sodium perborate (NaBO3.H2O) provides better improvement in the reactive process and is better seen, particularly under a white or luminescent light (Farrugia et al. 1). The Drunk Driver and Blood Analysis In looking at other ways, or other reasons for testing blood, alcohol levels in a supposed drunk driver, determine if the driver is driving over the alcohol limit and must be taken off to jail. Most legal jurisdictions will follow the American Society of Crime Laboratory Directors/ Laboratory Accreditation Board (ASCLD/LAB) in any type of blood alcohol testing, particularly where uncertainty calculations are to be performed (Gullberg 153). The standard limit for alcohol levels in a blood test are .08g/100 mL, or more. While Breathalyzer tests are still used, there have been some incidences where it has been inaccurate, and therefore, the blood test is considered to be the more accurate of alcohol measurement in the blood. A Standard Deviation (g/100ml) plot is shown below for a single observation against concentration. It represents a linear regression equation from the uncertainty function in the total method variability in function concentration (Gullberg 156). (Fig. 4, Gullberg 156) It is very important to understand measurement uncertainty in blood toxicology analysis and to also report it along with the findings in analysis, to ensure fitness-for-purpose and accompanying confidence levels (Gullberg 160). Essentially, the basic model is that the coefficient of variation within uncertainty is generally, 1-3%. Conclusion Conducting scientific analysis of blood in crime scenes and in drunk driving cases, provides a public service in finding the truth of who is truly guilty of a crime, or not. Scientific analysis, in such cases, showcases blood as the variable which tells the truth of a situation and provides justice. Therefore, scientific analysis must be conducted properly, using the scientific standards that also hold up in a court case and cannot be disputed. As methods of DNA analysis also develop over time, this has been one of the biggest areas in providing truth in evidence through scientific analysis. It all starts from the first drop of blood. Resources Farrugia, Kevin J., Kathleen A. Savage, Helen Bandey, Tomasz Ciuksza, and Niamh Nic Daeid. “Chemical Enhancements of Footwear Impressions in Blood on Fabric – Part 2: Peroxidase Reagents.” Science and Justice. (2011): 1-12. Doi: 10.1016/j.scijus.2010.11.002. Gullberg, Rod G. “Estimating the Measurement Uncertainty in Forensic Blood Alcohol Analysis.” Journal of Analytical Toxicology. (2012): 36: 153-161. . Muirhead, Kirsty. “Biomarkers Leave Gender Clues at Crime Scene.” Chemistry World Online. Web. 15 January 2014. . NSFTC. “A Simplified Guide to Bloodstain Pattern Analysis.” National Forensic Science Technology Center (NFSTC). 2009. Web. . Read More