The use of DNA to exonerate an individual under the post-conviction Essay

The use of DNA to exonerate an individual under the post-conviction use of DNA evidence or the evaluation of blood-alcohol level - Essay Example Generally, to be admissible the scientific evidence must have probative value. To add, the evidence has to be shown to have sufficient basis to produce uniform and reasonably consistent results that influence materially to the ascertainment of truth. Like all other criminal cases, the prosecution in DUI offences, have the duty to prove beyond the reasonable doubt that, at the time of the offence, the accused blood alcohol concentration was beyond the statutory limits (levinson D 2002). In most jurisdictions, the statutory limit range from 0.08% to 1%. Consequently, it is crucial for the prosecution to obtain biological samples, for example, blood, urine or expired air that would conclusively prove that the accused blood alcohol level was beyond the statutory limit. Therefore, forensic evidence is paramount, to show that the real blood level concentration, that it exceeded the limit. To obtain the blood alcohol concentration, police extracts body substances of the suspect which they s ubject to testing. However, in the field, it is impractical to obtain and test blood and urine sample due to the expertise and time required. Therefore, police rely on the use of breath testing devices, (of which breathalyzer is one the various types.), since they are easy to operate, precise and reliable in the field. The breathalyzer operates through testing of the suspect’s expired breath or the alveolar air. It operates on henry’s law that states that at, a constant temperature and pressure, the concentration of a gas that has dissolved in a liquid is proportional to the concentration of the air that is directly above it. Therefore, the alveolar air expired is usually at equilibrium with blood. Consequently, the breathalyzer works on the assumption that the alcohol concentration in the alveolar air has a direct relationship with the blood alcohol concentration, BAC. Upon consumption, alcohol is neither digested nor chemically altered in the circulation. While the b lood passing through the lungs, some of the alcohol passes through the membrane and into the air sacs (alveoli) in the lungs, and it evaporates since it is volatile. Therefore, it mixes with the alveoli air, which is subsequently exhaled. Hence, the concentration of alcohol in the air sacs is equivalent to that in that, in the blood. The exhaled air is the one that is detected by the breathalyzer. The alcohol concentration in the alveolar air exhaled is then augmented by a factor referred to as the partition ratio. This is done to relate the reading to BAC, through conversion of the concentration measured in the breath to the matching alcohol concentration in the blood. The breathalyzer works on the assumption that the ratio of the ratio of breath alcohol to blood alcohol is 2100:1. This means that the concentration in every 2100 ml alveolar air is equivalent to that in 1Ml of blood (Begleiter H, Kissin B 1996). The breathalyzer has a mouth piece through which the suspect blows the exhaled air and a sample of the same goes to the sample chamber. What follows is a series of chemical reactions. The breathalyzer contains a system to sample the breath of the suspect, 2 glass vials that contain chemical reaction mixtures, and a series of photocells joined to a meter to that measures the color change that results from the chemical reaction. For effectiveness, the breathalyzer must be administered by a qualified operator and