Question: How do people's fingerprints differ? Are there any big differences (noticeable to the eye)?

Richard Case answered on 15 Jun 2011:

Excellent Question janieolver…. I will try to explain,

The tip is… the closer you look at something the more individual and unique it is..

There are 3 levels of detail when looking at fingerprints….

1st Level – Fingerprints can be divided into different patterns – Arches, Loops, Whorls, Composites (main ones). Here is a link to a good easy-to-understand page on the patterns http://ridgesandfurrows.homestead.com/fingerprint_patterns.html

You can see these patterns without having to use a magnifying glass.

So… if I find a fingerprint at a murder with a loop pattern, I can immediately say that all the criminals that didn’t have loop patterns did not commit that crime.

2nd Level… If you look more closely at a fingerprint (you can use one of the images on that link), you will see that it is made-up of lots of lines (ridges). If you follow these lines you will notice that they sometimes stop or split into 2. We call these “charateristics”. We can look at the characteristics in 2 fingerprints, and if they appear in the same place on both and there are none out of place, then we can say they are a match. This is the way fingerprint experts identify the criminals. This is best done using magnification. The tools we use are:

Magnifying Glass http://www.waproducts.co.uk/proddetail.php?prod=SPFP100
Comparator http://www.fosterfreeman.com/index.php?option=com_content&view=article&id=19&Itemid=48
IDENT1 (UK Fingerprint Computer) http://www.npia.police.uk/en/10504.htm

3rd Level – If you look at a fingerprint through a microscope you will notice little dots on the lines. These dots are sweat pores. This is where the sweat comes out of the body. The shape and sequence of these pores are as unique as characteristics. Also the lines (ridges) are uniquely shaped too. These techniques are very rarely used.

So to try to put these into a scenario:

You have in your hand a photo of a tall man

You see a line of 20 people in the distance, which includes that person. You can already eliminate all the women and the short men (1st Level)

You now move closer to the 5 people you have left. You can now eliminate 3 more due to more detail such as hair colour and eye colour (2nd Level)

You now have a pair of identical twins which look like the person on the picture. You now need to look at them very, very carefully and by using tiny details such as freckles or a missing tooth you can finally say for certain which one is the man in your picture (3rd Level).

I hope this helps 🙂