Analysis
Analysis of trace materials most often begins with a visual examination of the evidence usually involving macrophotography. This is then usually followed by microscopic analysis, of which a number of different types are available depending on the type of material to be analysed, such as a stereomicroscope, scanning electron microscope (SEM) or comparison microscope. SEM is especially useful because X-ray analysis can be conducted on selected areas of the sample, so is a form of microanalysis. It is useful where chemical residues can show unusual elements present which may indicate chemical attack of the product. A car accident caused by a diesel fuel leak, for example, showed traces of sulfur on the cracked tube indicative of attack by sulfuric acid from the battery.
Gunshot residue may be identified by elemental analysis using atomic absorption or with a scanning electron microscope equipped with an energy dispersive spectroscope. Small amounts of explosives, volatile hydrocarbons, and other chemicals are identified with the use of analytical instruments, such as gas chromatography, mass spectrometry, and infrared spectroscopy, all of which separate out the components of the chemicals.
Similar comments apply to damaged items from an accident scene, but care is needed in ensuring that the sample is not damaged by the testing, or sampling for testing. Such nondestructive testing must always be used first before considering destructive methods which involve taking small samples from the item for more detailed tests, such as spectroscopic analysis. Use of all such methods must be done in consultation with other experts and the relevant authorities, such as lawyers on both sides of a case.
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Famous quotes containing the word analysis:
“Ask anyone committed to Marxist analysis how many angels on the head of a pin, and you will be asked in return to never mind the angels, tell me who controls the production of pins.”
—Joan Didion (b. 1934)
“... the big courageous acts of life are those one never hears of and only suspects from having been through like experience. It takes real courage to do battle in the unspectacular task. We always listen for the applause of our co-workers. He is courageous who plods on, unlettered and unknown.... In the last analysis it is this courage, developing between man and his limitations, that brings success.”
—Alice Foote MacDougall (1867–1945)
“Analysis as an instrument of enlightenment and civilization is good, in so far as it shatters absurd convictions, acts as a solvent upon natural prejudices, and undermines authority; good, in other words, in that it sets free, refines, humanizes, makes slaves ripe for freedom. But it is bad, very bad, in so far as it stands in the way of action, cannot shape the vital forces, maims life at its roots. Analysis can be a very unappetizing affair, as much so as death.”
—Thomas Mann (1875–1955)