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Forensic chemistry is mainly understood as the study and application of extensive continuum of the present chemistry to answer questions of interest to a legal system (Lucas, 1935). This may majorly be in relation to a civil action or a crime. It majorly concentrates on analyzing a crime scene and provides the way forward to a crime scene that happened before (Bell, 2006).
Under certain conditions, forensic chemistry may be considered as the study of recognition and identification of illegitimate drugs, accelerants used in combustible cases, explosive and gunshot residue (Bell, 2006).
A student is required to inspect two bags of metallic debris. The bags indicated as A, B, C, D (prime) are from the crime scene while the corresponding bags without prime are from the person of interest . Sample A-D are not the same, and do not represent the same person of interest and, consequently, you are on your own with each set of samples. The crime scene debris is the same in all cases (Bell, 2006). The amounts of material in these bags are far in excess of that which would be expected to be recovered from a person of interest. Nevertheless, the same principles of investigative practice can be used on this material as in a real crime scene investigative scenario (Lucas, 1935).
This report has mainly focused on acquiring chemical statistics for samples of metallic fragments recovered from both, person of interest and the crime of scene, in order to be able to establish if the person of interest has been present at the crime scene. In case, the person has been present, he is in possession of any material present at the crime scene and, thereby, explicitly link the person of interest back to the crime scene and the crime, as he will eventually assist in their assurance (Newton, 2007).
After the separation and labeling of the metal debris, the samples were weighed accurately. 0.2g of the weighed samples were taken and placed into 50ml clean beaker. 2ml if nitric acid and 6ml of hydrochloric acid were added and the entire sample was placed on a 100degrees hot plate to evaporate the contents to dryness (Newton, 2007). After the completion of the digestion, 2ml of hydrochloric acid and about 4milli distilled water was added and thawed for about 3 minutes. The samples were then passed through a filtered paper into a centrifuge tubes and then topped up to 12g with milli Qwater.
All the samples were then analyzed by ICP-MS and ICP-AES, after being diluted to appropriate concentrations. The diluted concentration was 2% nitric acid in milli Qwater and 2ppbrhodium and iridium as internal standards (Newton, 2007).
Both inductively coupled plasma, mass spectrometry (MS) and atomic emission spectrometry (AES) are a simultaneous spectrometry. However, ICP-MS involves the determination of a range of metals (Newton, 2007). Spectrometry uses to produce excited atoms that emit electromagnetic radiation of a particular element. This emission is indicative of the concentration of the metal within the sample. The low concentration can be achieved by ICP-AES is one part per billion (ppb)
Concentration of the samples from crime scene in part per million
According to the results presented above, all the student ICP-AES silicon samples were not close. The student samples that were close were the titanium samples.
On analyzing the POI and CS graph for concentration of different contents, the graphs tend to be symmetrical. It clearly shows that the samples contained equal amounts of silicon, scandium, manganese, and gallium. There is maximum concentration of both POI sample and CS sample, which is clear evidence that the person of interest was present at the crime scene.
High concentration in brasses
From the above table, the students results for CS concentration of brasses were almost they slightly differ from those of POI concentration though with a small margin.
As seen from the graph above, the graph for each and every concentration have a similar pattern illustrating that the person of interest was present at the crime scene.
High concentration in Al
From the above data, all the results are almost equal for both POI and CS concentration in aluminum. There is only a slight difference that is seen in chromium.
The curves for both POI and CS follow the same trend and do posses the same concentration for both the contents of the samples.
After carefully analyzing the results, it is depicted that the person of interest was present at the scene of crime. This is evidence from the view of the material in possession had a close concentration as those at the crime scene.