Fingerprints
When you think of forensic science, surely fingerprinting comes to mind? To be fair, there is a lot more to it than that! But fingerprint analysis is probably the most well known use of forensic science. Over the last 100 years it has become the main method of identifying criminals. Of course now we’ve moved forward with DNA analysis. But let’s take a look at these things called fingerprints...
Fingerprints are the tiny ridges of skin on a finger which make a pattern that is different from any other in the world. Even identical twins have different fingerprints. They can therefore assist a detective to work out who has been at the scene of a crime.
The ridges of a fingerprint develop in the womb and remain the same throughout life. Although people grow and increase in size, the ridges became permanent and fixed in their patterns from about 17 weeks of embryonic development. Ridge patterns do not change like other parts of our bodies.
A fingerprint is composed of grease and dried sweat left behind by the tips of the fingers. They can be detected on a vast range of different surfaces using a variety of techniques. The police keep a huge national database of prints taken from charged criminals. Going, going, gone are the days of using ink - new prints are taken by a laser scanning procedure where the hand is placed on a flat glass plate and its print is stored and compared to other prints electronically.
Fingerprint Characteristics
Fingerprints fall into three large general groups of patterns: arches, loops, and whorls. 60% of people have loops, 35% have whorls, and 5% have arches. Each of the three pattern types have focal points which are used for classification.
In the loop pattern there are two focal points, the core and the delta. The core is the centre of the loop, whilst the delta is the area where there is a triangulation or a dividing of the ridges. A whorl pattern will have two or more deltas, and the arch pattern has no delta or core. Naturally, however, it’s not quite that simple, as there are different arches, different loops, and different whorls...
Plain arch: the ridges enter upon one side, make a rise or wave in the centre, and flow or tend to flow out upon the opposite side.
Tented arch: the ridges feature a sharp up thrust.
A loop is that type of pattern in which the ridges enter upon either side, recurve, and pass out from the same side they entered. The terms ‘radial’ and ‘ulnar’ are used to indicate which side of the finger the ridges enter and pass out, derived from the radius (thumb side) and ulna (little finger side) bones of the forearm. It should be noted that if someone says “Oh look, that’s a radial loop” etc., they also need to stipulate right or left hand, as a left handed radial loop will look just like a right handed ulnar loop.
Plain whorl: consists of one or more ridges which make or tend to make a complete circuit, which crosses a line drawn between two deltas.
Central pocket whorl: consists of at least one recurving ridge, or an obstruction at right angles to the line of flow, with two deltas.
Double loop whorl: consists of two separate loop formations, with two separate and distinct sets of shoulders and two deltas.
Accidental whorl: consists of a combination of two different types of patterns or does not conform to any of the definitions.
Types of Fingerprint Evidence
Patent prints - prints that are clearly visible, made by touching something like paint or blood and then touch other surfaces.
Latent prints - formed when you touch something and the natural oil and sweat on your hand leaves a print, and mostly invisible to the naked eye (although fingerprinting dust makes them visible).
Physical prints - made when you touch something like gum that leaves a clear impression of your prints.
So there you have it - now watch what you touch!!! ;)