Fiber Analysis

As we know fibres are what make up all of the clothes and textiles around us. Some find it very surprising to know that the analysis of fibres is a very useful technique to the forensic scientist. The presence of fibres is highly useful as it is another way of linking criminals to crime scenes or victims or other pieces of evidence.

Fibres are classified as either natural or synthetic, though most fibres around these days are synthetic. Fibres are probably one of the most useful pieces of evidence that can be collected at a crime scene - they are easy to handle and maintain. There are also large reference collections around to compare the fibres to, meaning any fibres found at a crime scene can be identified. Though fibres may seem the same colour to the human eye, this may not be the case.

We need to look at the fibres more closely, so forensic scientists use Microspectrophotometry. This is a microscope linked to a spectrophotometer (which is a device that measures light wavelength). Light wavelengths are passed through the fibres, though some are absorbed, showing its pattern clearly. This is how we can establish whether two or more fibres came from the same source. This method is widely used, as it does not damage the evidence. Another way to compare the fibres is to look at their chemical compositions. This is done by gas chromatography. The fibre is subjected to this gas chromatography, and the fibre is decomposed to gas and analysed. However this is very destructive to the evidence.

Hair Analysis

Hairs, whether they be human or animal, are almost always found at a crime scene. Hairs fall off the body naturally every day, so it is understandable that hairs will be found anywhere. The structure of a hair is quite simple. It consists of the inner core (medulla), the surrounding layer (cortex), and the covering "skin" (cuticle). The cuticle resembles a series of overlapping scales, which can be compared. Though there would never be an exact between two hairs, these can help in comparing hairs.

When forensic scientists are comparing hairs in the lab, they are compared under the comparison microscope, which allows two samples to be viewed at the same time, therefore making comparison easier. It is often misinterpreted that hairs can be an exact match, but this is incorrect. No two hairs are alike, even two hairs which came from the same person. Though there may be very noticeable similarities, there would be no "match". However if two hairs are very similar it does usually stand up in court, as it would be very unlikely the two very similar hairs came from different people.

Hair can also be useful in DNA fingerprinting. DNA can almost always be extracted from the hair one way or another. If a hair as been forcibly removed, it will hold the hair root and also some tissue on the end. If a hair has fallen out naturally, just the root will remain on the hair. Both the small collection of tissues and the root are ripe for DNA profiling, obviously useful in some criminal investigations. DNA can also be extracted from the hair itself. The hair contains mitochondrial DNA, which can be extracted and compared to other samples.