CSI And Metals
How does the analysis of metals help in CSI?
First, we will identify the major composition of the metal. Is it lead? Copper? Then, we will also look to see what the trace elements are that are present in the metal, because all elements are not pure. They contain minute amounts of other elements, other metals, in concentrations that are a percent or less. They do not mean much in terms of the utilization of the metal, but they mean a lot when it comes to comparing that metal to another metal, because those minute traces of elements, or trace elements, serve as a fingerprint for comparison purposes. They are very important points for comparing trace elements, or trace metals, in the forensic analysis.
How is metal identified and compared in CSI?
The first thing that you're going to do is you're going to look for the major constituents of the metal. Is it copper? Is it lead? We use a variety of analytical techniques that are available to us. Spectral photometric techniques, X-ray technology techniques are quite prevalent in, or pretty much available, to crime labs for looking at the major constituents of metals. When it comes to looking for the trace elements that are present in metals, the thing that gives metal its fingerprint, "fingerprint characteristic" requires sensitive technology. The crime labs must call upon equipment that has a high degree of sensitivity that can seek out and identify trace elements and trace metals that are present at concentrations of a percent or less. They serve as a fingerprint for comparing one metal against another.
How does the analysis of paint help in CSI?
There are two areas of investigation that relate to paint analysis. The first is the "hit and run". The deposition of motor vehicle paint on the victim's body or clothing. Or, just being left behind somewhere at the hit and run scene, offers clues as to the vehicle that was involved in the accident. If the vehicle is a hit and run, we may be able to identify the make and model of the paint by examining its color and its layer structure. Many crime labs have access to vast libraries of automotive paints that allow for the identification of make and model. With respect to the automobile, what's important, what's critical, in analyzing automobile paint is color and layer structure. There's a tremendous variety of automobile paint colors. Tremendous variety when it comes to the underlying layers. Of course, there's the clear coat which is a top-layer of paint on the automobile which has no color. It still offers a point of comparison, when analyzing the chemistry of automobile paint.
How does the analsyis of paint help in a car crash investigation?
Well paint is first subjected to a low powered microscopic examination where we will look at its surface features color and underlying color layers if any do exist. Once that is accomplished, we will then look at the chemistry of the paint. Paint is what we call a polymer. It is a special type of chemical which can be characterized in a crime lab by a number of analytical techniques. So in a nutshell what we look for is color, layer structure and chemistry of paint. The first and probably the most important tool is the old fashioned microscope low powered stereoscopic microscope is what we first call up on to examine a paint chip.
How does the analysis of paint help forensic scientists in a burglary investigation?
Another area where paint analysis comes into play is in a burglary. So a burglary may be committed and some paint from a wall may come off onto a tool that a burglar may use. In trying to link that tool to the commission of a particular burglary, if you look at the colour of the paint, the chemistry of the paint, compared to the paint coming off the wall. In respect to the automobile, what's important, what's critical in analyzing automobile paint is colour and layer structure. There's a tremendous variety of automobile paint colours, a tremendous variety when it comes to the underlying layers. Of course there is the clear coat, which is the top layer of paint on the automobile which has no colour, but still offers a point of comparison when analyzing the chemistry of automobile paint.
How does the analysis of soil evidence help in CSI?
Surprisingly so, the most important characteristic of soil is it's color. There are many thousands of different soil colors that exist on our planet, and just comparing the colors of soils provides very significant insights into how closely they compare. Once we complete the color comparison, we will then go on and look at the mineral content of soil as well as the rock content of soil. That part requires the input of a forensic geologist.
How is soil identified and compared in CSI?
That's a very good question because one of things that's important in ascertaining the value of the soil examination is its diversity at the crime scene. For example, if a crime scene takes place on location x and all the soil within a mile of location x is indistinguishable, is the same, the value of that soil as forensic evidence is slight. So what you want to do is to show that there's a tremendous or significant variation of soil at the crime scene. So if we have soil at location x and we have a shoe worn by the suspect with soil on it and they both compare with respect to their colour, mineral content, rock content, then we go a hundred feet out in all directions - north, south, east, west - and we collect soil and we find that those soils are different. Then we go maybe another 300 feet out and we do the same and we find that those soils are different, what we've really done is narrowed down that comparison down to a very small area of the crime scene. It eliminated the possibility that those soils could have come from outlying areas.
