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What are fingerprints?

We look at fingerprints, what they are and how they are formed.
This video will cover the difference between fingerprints and fingermarks and how the fingerprint patterns are formed during gestation. On our fingers and toes there are many fine ridges. These ridges form recognisable patterns and are formed during the gestation period of the foetus during pregnancy. Fingerprints are produced from the contact between the ridges present on our fingers and a surface. The transfer is achieved by the deposition of the secretions from our glands associated with the ridges on our skin or by contaminants present on the finger surface. These ridges are more commonly referred to as friction ridges, as it is suggested that their primary purpose is to enhance grip. In forensic science, we use the terms “fingerprints” and “fingermarks.”
There is a difference between the two terms. A “fingerprint” is used to describe a fingerprint in which the source of it is known. For example, if you were arrested by the police, they would take your fingerprints. “Fingermarks” are used to describe the ridge pattern found on surfaces where the source is unknown. For example, fingermarks left at crime scenes where the source is unknown. As such, there is a difference in the quality and clarity of fingerprints and fingermarks. Fingerprints will be of a good quality, showing all the ridge detail and would ensure that all detail was recorded. Whereas fingermarks are generally of poorer quality, as they could be incomplete and smudged.
Fingermarks are frequently found at crime scenes or on objects associated with a crime such as a knife in an assault case. They can provide identification, not only of an individual, but of a particular finger on the individual’s hand. Fingerprints and fingermarks can be stored on and retrieved from databases, which facilitates ongoing and future investigations. Until the advent of DNA profiling, the use of fingerprints was the main means of human identification in criminal cases. However, DNA profiling cannot distinguish between identical twins. Whereas fingerprints can. The skin over most of the body is relatively smooth, but friction ridges are found on the fingers and palms and soles of the feet. Friction ridge skin evolved in primates, so even gorillas have fingerprints.
The development of friction ridge skin is initiated at a very early stage in foetal growth. The development of the foetus is charted in terms of its Estimated Gestational Age or EGA. At around five to six weeks EGA, the foetus’s hand will start to develop, with fingers developing at approximately six to seven weeks EGA. At that time, volar pads appear on the palm, which are swellings of mesenchymal tissue. By 16 weeks EGA, the mesenchymal tissue swelling is invisible as the growth of the hands has enveloped the pads. It is in weeks 11 to 20 EGA, that the fiction ridge development occurs, with the volar pads providing the bedding for that development.
Primary ridges on the dermis, with fully formed ridge endings, are the first to develop. These can be thought of as ridge units, as each are associated with a sweat pore. During the development, ridges will start to become visible from the apex of the finger, the tip of the finger, and the distal interphalangeal flexion crease, which is the first joint underneath the apex of the finger. The developments of the ridges from the three different regions occur at different speeds until they converge and cover the dermal surface. Between weeks 15 to 17 EGA, secondary ridges start to develop between the primary ridges and continue until week 24 EGA, when the development of the dermis is complete.
These friction ridges do not change in the person’s lifetime. Only injury, disease, and decomposition after death will change the friction ridge pattern. These friction ridges can be classified into three levels of detail. First level detail refers to the overall pattern. Second level detail refers to the major path deviations, or minutiae, as they are commonly called. And third level detail refers to the intrinsic ridge formations. These levels of detail are used in identifying individuals from their fingerprints. You will find out more about fingerprint identification in a later video. Try this. Place your hand, palm-side up, so that the back of your hand is touching the table and slide your hand along the table.
Now, flip your hand so your palm is touching a table and slide your hand again along the table. Did you notice a difference? It should be more difficult to slide your hand along the table palm-side down. This is due to the friction ridge skin on the palm of your hand. By watching this video, you should now be able to– understand the difference between fingerprints and fingermarks, describe how fingerprints derive from friction ridge skin, and describe how friction ridges develop during gestation in pregnancy.

We begin with an introduction to fingerprints.

As a biometric, fingerprints were one of the very first methods used in police investigations and the possibility that they may be used as a means of identification goes back to around 1880 when Dr Henry Faulds (who studied at University of Strathclyde when it was know as Anderson’s University) is widely credited with first making the suggestion.

Here we’re going to look at some terminology and distinguish between fingerprints (known source) and fingermarks (unknown source). We will also explore how friction ridges are formed and you should look at chapter 2 and 3 of the US fingerprint sourcebook in the ‘see also’ resource link below to see some great images associated with embryonic fingerprint development. Chapter 1 of the US fingerprint sourcebook will also provide you with some more historical context for fingerprints and their examination.

The UK fingerprint source book also provides some historical information in chapter 2 as well as some general information about enhancement and visualisation of fingerprints.

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Introduction to Forensic Science

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