Biological Principles Flashcards
What is a fingerprint?
A fingerprint is an impression, left on a surface by someone’s finger, palm or foot - we use the term to include not only fingerprints, but also palm prints and footprints.
The skin on the undersides of our hands and feet is covered in intricate patterns of small ridges, called friction ridges, which enhance friction when gripping items.
When we touch a surface, the sweat and oils on these ridges are transferred to that surface, and under the right conditions, we leave a fingerprint which can be preserved and analysed.
You say fingerprints are unique and permanent; can you please elaborate on these two principles?
The patterns of ridges that form our fingerprints are completely unique due to countless developmental factors which influence the womb while we are developing as a foetus.
Our fingerprints are fully formed before we are born, and will remain in the exact same pattern and arrangement for our entire life.
How are fingerprints left, and subsequently located?
When we touch a surface, the sweat and oils on our skin are transferred to that surface, and under the right conditions, we leave a fingerprint which can be preserved and analysed.
Latent fingerprints are fingerprints that have been left at a crime scene - these fingerprints are usually invisible to the naked eye, and therefore require some form of enhancement in order to be visualised.
To locate and enhance fingerprints we use different types of powders and chemicals that react with the sweat and oils in a fingerprint to produce a visible fingerprint, and we can also use torches that emit UV and other colours of light, to help us locate and photograph fingerprints.
How do you know that no two people have the same fingerprints?
Are fingerprints always left when we touch a surface?
Fingerprints are not always left when we touch a surface - to leave a fingerprint there must be sweat, oil, or some other residue on our skin to be transferred.
Also, the surface being touched must be smooth and clean enough for a fingerprint to be left and later analysed.
Can you determine the age of a fingerprint?
There is currently no method for determining the exact age of a fingerprint.
There are however, indicators that may give a time frame as to when the fingerprints were left on a surface.
For example, cleaning a surface generally wipes away fingerprints; therefore any fingerprints located on a surface have been left since that surface was last cleaned.
How long do fingerprints remain on a surface?
The length of time a fingerprint remains on a surface depends on how well protected the surface is from weathering, and people touching and cleaning the surface.
For example, a fingerprint will last for a long time on a cup that is left undisturbed in a cupboard; however, fingerprints would not last on a cup that is frequently being used and washed, as those fingerprints would be washed off the cup.
What is a fingerprint composed of?
Fingerprints are most often composed of sweat and oils from our skin; as well as dirt and grease from our environment.
What chance is there that two people share the same fingerprints?
While it is possible to find two people who share very similar fingerprints, no two people share the exact same fingerprints due to the unique combination of genetic and environmental factors which influence the formation of friction ridge skin during foetal development.
Even identical twins, who present the greatest possibility of sharing the same fingerprints due to sharing almost identical genetics and the same womb during development, have different fingerprints due to slight differences in the way in which they interact with their womb environment during development.
Has fingerprint science been peer-reviewed?
All scientific research that is published in the field of fingerprint science is subject to peer review prior to publication.
