Archive for the ‘forensic science’ Category

Your Introduction to Fingerprinting

In forensic science on August 27, 2009 at 23:22

Fingerprints are a reproduction of the skin that appears on the palm side of fingers and thumbs in primates (humans included). The skin is organized into elevated friction ridges, which “appear to have evolved to assist in gripping”. (Bell, 2008, p.151)

There are two main premises that allow fingerprints to be used to identify individuals.

Firstly, formed before birth, the friction ridge pattern (or fingerprints) remains unchanged throughout the life of an individual (apart from growth, scarring/purposeful alteration). A fingerprints pattern arises from a layer in the skin (dermal papillae), which can survive even after death. (Jackson & Jackson, 2004)

Secondly, the ridge characteristics make individual fingerprints unique, and allow individualization with the probability of two matching prints at 1 out of 1 with 60 zeros. (Saferstein, 2004) Over the years, no two full prints have been found to be the same, (Jackson & Jackson, 2004) however, everyone has them.

To introduce, fingerprints can leave a trace upon contact with surfaces. Naturally, this is due to: the sweat that is released from the pores atop the ridges, present even after washing; and the oil that comes from touching oily skin (e.g. regions of the face). These prints are often accidently left by the perpetrators at the scene of a crime.

In most police forces around the world, it is common practice to record the fingerprints of  suspects and criminals. This is usually done through the use of inks, however, digital scans are also now being taken in the EU and US. Therefore, “due to recent advances in digital imaging, computer databases, and software, fingerprints can be cataloged and searched electronically”. (Bell, 2008, p. 151)

Putting fingers to faces

Putting fingers to faces

Once developed, the fingerprints from a crime scene are analyzed for possible matches. This can be performed with the aid of computer technology; however the final decision is made by the fingerprint analyst involved. Matches are identified according to uniqueness at certain points (minutiae). However, it should also be noted that in the UK, for example, there is no longer a minimum amount of minutiae needed for match (unlike the previous 16-point rule from 1953); the number of matching points needed to ascertain a match is at the discretion of the expert analyst, which can sometimes prove problematic.

Conclusively, “the technology associated with the collection of fingerprints is well developed, reliable and, in most cases, easily applied”. (Jackson & Jackson, 2004, p.35)

– Bell, S. (2008) Encyclopedia of Forensic Science. New York: Facts On File, Inc.
– Jackson, A.R.W., Jackson, J.M. (2004) Forensic Science. Harlow: Pearson/Prentice Hall.
– Saferstein, R. (2004) Criminalistics: An Introduction to Forensic Science, 8e. New Jersey: Pearson/Prentice Hall.