Types of prints.
A print is not only made of a collection of lines but the all the lines together
make a special figure. And there are not so very much different figures as you would presume. There are about 7 different types as you can see down here:
- Arch: The lines are going like waves from one site to the other site.
- Tentarch: Like the Arch but with a rising stick in the middle.
- Loop: The lines coming from one site returning in the middle to the te same
- Double loop: Like the loop but with two loops inside, one standing one
- Pocked loop: Like the loop but with a small circle in the turning point
- Whorl: The lines are making circles
- Mixed figure: Composed with different figures
But in every type of print there are lots of differences, the number of lines, their shape or their size make every figure different. Typica.
A fingerprint contains a lot of typica, unique lines. They are short or long, they can start, stop or split, they make figures, can be big, small or broad.
And above all it can happen at every place. So now you can imagine that no two fingerprints are the same. It is a little bit like a living-room, in all the world there will be no two the same living-rooms. Flowers, paintings, pictures, trash, furniture and music will make every living-room unique!
Here you see a part of a fingerprint.
Generaly there are two kinds of real typica:
- Ending lines
- Splitting lines (bifurcations)
Above that there are a lot of other differences made up by those two typica: a very short line between two other lines is called an "isle", when a line splits and immediately returns to one line it is called an "eye". When it splits and one of the two splitting lines immediately returns to the site it came from and stops it will be called a "hook". A lot of times one can see small lines or lineparts between two friction ridges. It looks a little like newborn lines, and in some rare cases it is seen that such a line became greater in a few years. But that are always very small parts of lines.
Fingerprints are made of ridges on the upperskin on hands and feet of all people and some animals. These ridges make lines of different size's and forms. Everytime a line stops or splits it's called a typica. The amount of typica (with no difference) make's it an identification or not. The amount of typica is in many country's different. In Holland
10 to 12 characteristic points are
required with no difference.
There are 2 rules where the science of fingerprints is based on:
1) They are "permanent" in that they are formed in the fetal stage,
prior to birth, and remain the same throughout lifetime, barring
disfiguration by scarring, until sometime after death when
decomposition sets in.
That means that the prints do not change during a life time. That's
not all true because fingerprints do change, but the changes can be
explained. If not, they can't be identified. The changes can be made
by: flexibility from the skin, growing, a dirty finger, scarring, a wound,
or a disease of the skin.
2) They are "unique" in that no two fingerprints, or friction ridge area,
made by different fingers or areas, are the same (or are identical in
their ridge characteristic arrangement).
People always ask if identical twins have the same prints, the answer is NO.
They have completely different fingerprints, although they have the same DNA.
Some people think that it is because there is a influence of the environs that
make the prints develop different.
There is never found a print that is the same, even not on the same person.
The databanks of fingerprints all around the world, are containing milliards of unique prints!
Worldwide there is no same rule when a identification can be made.
In the Netherlands we require 12 characteristic points, In South-Africa 7 points will make a identification, And in a lot of countries (England, America) there is no rule, the expert decides.
Transmitting prints to a object.
- The most common way is leaving fat from the finger on the object.
- It is also possible that Amino-acids from the finger leave their marks.
- A finger can make a "stamp" in a soft underground like putty.
- A mark can be made by a substance on the finger like blood or paint.
Making marks visible.
There are a lot of ways to make marks visible. In fact a lot of marks can be seen if you look good. Just put a finger on a window and take a good look at the window. With the right light you can see the mark. It can be seen because grease from the fingertip puts a "stamp" of the finger on the glass. It will not be there forever because it simply will dry out. But there always will be a small residu left, if the object is not cleaned. Fresh fingerprints can be found and made visible with powders that will stick on the grease of the finger. It are very fine powders, mostly is used aluminium powder.
The underground on which the print is put on is very importend for the way the prints must be made visible. When a print is put on a piece of paper it is possible to make it visible with a magnetic iron powder. Strictly speaking the powder is not magnetic but the lifting brush is. This can only be done on very fresh marks, not much older than a few hours. Afther that an other method must be used:
Ninhydrin. It is a chemical that colors the Amino-acids that are left behind after contact with the skin.
In a lot of cases involving metal or plastic objects the cyano-method can be used. When a few drops of superglue,
cyano-acrylate, are heated they vaporise. The smoke of the cyano will attach to the fingerprints leaving a clear white print. It must be done in a special space under special conditions.
Do never try this at home because it is very poisonous!
Saving the marks.
It is possible to save the marks, for further investigation, by making
photographs of it, storing it on rubber lifters or tape, keeping the original
underground or copying it.
Down here you can see how fingerprints on a bottle are made visible with a brush and aluminium powder. A black rubber lifter is installed over the prints. After removing the black lifter, a copie of the prints is made. A plastic sheet is placed over the prints so they would not be damaged. The prints are now usable for further investigation.