The Effect of Fingerprint Similarity Between Siblings and Non-related People

Researched by Hannah R.


The purpose of this experiment was to compare the similarity of fingerprints between siblings and non-siblings.

I became interested in this idea when I was looking at my sister’s and my fingerprints last year and I noticed how they looked a little bit alike.

The information gained from this experiment could help police to determine criminal’s fingerprints by looking at some of their family member’s.  If my hypothesis is correct it could also help orphans find their biological parents.


My hypothesis was that siblings would have a higher percentage of similar type fingerprints than people who are unrelated.

I based my hypothesis on an article I found in World Book Online by John Thornton.  He stated, “Although no two fingerprints are alike, families have the same style of fingerprints (loops, whirls, arch, or abstract).”


The constants in this study were:
•    Same fingerprinting tools used
•    Same finger used for printing
•    Same jewelers’ loupe used for studying
•    Same method of printing

The manipulated variable was the hereditary relationship of the subjects.

The responding variable was the similarity of the fingerprints.

To measure the responding variable, I classified the fingerprints and compared the similarity for people who are biologically related to those who are not.


1 Ink pad
1 Roll of fingerprint squares
1 Bottle of ink remover
1 Jewelers’ loupe
1 Ink roller




1.    Get a fingerprinting kit.
2.    Obtain subjects.
  a)    25-30 biological siblings.
  b)    Non-related people must be expanded past cousins in a family.
3.    Take fingerprint samples.
  a)    Spread ink on the pad.
  b)    Spread thinly with brayer.
  c)    Roll 1 finger.
  d)    Print 1 finger.
  e)    Repeat with all fingers on both hands.
  f)    Label all with this subject’s code.
4.    Study fingerprint samples for one individual.
  a)  Classify the prints as loop, whorl, arch, or abstract.
  b)  Record  data for this individual.
5.    Repeat step four for all individuals
6.    Determine the percentage of fingerprints that are alike within each sibling group.
7.    Label group.
8.    Write down the conclusion.
9.    Repeat steps a-e until all sibling groups are completed.
  a)    Separate the fingerprints from their matches.
  b)    Put a fingerprint sample with one that doesn’t match it (Example: 7a with 5b)
  c)    Classify the prints as loop, whorl, arch, or abstract.
  d)    Determine the percentage of fingerprints that are alike in that group.
  e)    Label group.
  f)    Write down conclusion.
  g)     Shred fingerprints.
  h)    Repeat steps a-f until all non-related groups are complete.


The original purpose of this experiment was to study the effect of similarity of fingerprints in a family.

The results of the experiment were that the siblings had a higher percent of fingerprint similarity than of those who were unrelated.

See the table and graph below.


My hypothesis was that siblings would have a higher percentage of similar type of fingerprints than people who are unrelated.

The results indicate that this hypothesis should be accepted, because they show that the groups of siblings had a higher similarity rate than those of the people who were not related.

After thinking about the results of this experiment, I wonder if parents share the same type of fingerprints as their children.

If I were to conduct this project again, I would have taken more fingerprint samples. Also, I would have made more trials for the experiment.


Definition Of A Fingerprint   
There are four main types of fingerprints, loops, whorls, arches, and abstract. However, no two fingerprints are alike. A fingerprint is a pattern of marks in ink of the lines on the tip of a finger used for the purpose of identification.

What Is Fingerprinting
Fingerprinting is the process of identification based on the impressions of the ends of the fingers. The impressions consist of patterns formed by ridges that cover the skin of the fingertips. Fingerprints provide one of the most reliable methods of identification. No person’s fingerprint is identical to any other human being. In most cases, fingerprints remain the same throughout any person’s lifetime. Ridges on the person’s fingerprints only change as a result of surgery, disease, or an accident. 

The Use Of Fingerprints
Fingerprints are often used in the investigation of crimes. Prints found at the scene of a crime may help identify the subjects. Fingerprints that match police records are strong evidence in court. Fingerprinting may help prevent crime. For example, banks, military bases, and government buildings use computers to check fingerprints of employers before they can be admitted to different areas. A number of states allow children to be fingerprinted to help identify them if they are later reported missing.

How To Take Fingerprints
Fingerprints are recorded by rubbing the finger in special ink and pressing down on a white card, producing a copy of the prints. Fingerprints are either visible or they’re not. Most visible fingerprints are soiled with blood, dirt, or other substances. Non-visible prints (latent) are made by perspirational oils that exist naturally on the fingers. Visible prints can be photographed immediately. Latent prints must be developed first. Police use colored powder to develop most latent prints found on non-absorbent surfaces like wood or metal. The powder is brushed onto the surface and sticks to the oils in the print. The prints are then lifted from the surface by pressing sticky tape to the print. The prints are then photographed from the tape.

Types Of Fingerprints
There are four main types of fingerprints. In the most common pattern, the loop, ridges begin on the side of the finger, curve back sharply, and end on the same side. Ridges in the whorl pattern have a circular form. In the arch pattern, the ridges extend from one side of the finger to the other with a rise in the center. Abstract prints are a combination of all of these patterns.

Before the development of fingerprinting, people identified criminals and slaves by branding them, tattooing, or even amputating a limb. Other early methods of identification were less reliable but more humane. It included photography and the Bertillion system, a technique based on measuring the arms, legs, and other body parts. 

When Fingerprinting Began
Fingerprinting became the scientific method of identification in the 1880’s with research of Sir Francis Galton, a British anthropologist. Galton mathematically calculated that no two fingerprints are the same. During the 1880’s, two police officers, Juan Vucctich and Sir Edward R. Henry, developed fingerprint systems. The Henry system became the basis of fingerprint system used in the U.S. and other countries. Today, newer systems use computers to classify and compare fingerprints. Some crime laboratories also use evidence from DNA. This evidence is based on analysis of a genetic material taken from samples of blood, hair, and other biological substances. This evidence is used to make identifications in civil and criminal cases.

Famous People In Fingerprinting History
1686-Marcello Malpighi
Marcello Malpighi, a professor of anatomy at the University of Bologna, noted ridges, spirals, and loops in fingerprints. He made no mention of their value as a tool for individual identification.

1823-John Evangelist Purkinji
John Evangelist Purkinji, professor of anatomy at the University of Breslau, published his thesis discussing nine fingerprint patterns, he too made no mention of the values of fingerprints for personal identification.

1856-William Hershel
The English began using fingerprints in July 1858. Sir William Hershel had Rajyadhar Kona, local businessman; impress his handprint on the back of a contract. This idea merely frightened him out of any thought of repudiating his signature. The natives suitably impressed, Hershel Made a habit of requiring palm prints and later, prints on the right index and middle finger on every contract made with the locals. Personal contact with the document, they believed, make the contract more binding than if by simply signing it.  As his fingerprint collection grew, Hershel began to note that inked impressions prove or disaprove identity. While his experience with fingerprints was limited, Hershel’s private conviction that all fingerprints are unique to the individual as well as permanent throughout that individuals life, inspired him to expand their use.

1880-Henry Faulds
In the 1870’s, Dr. Henry Faulds, British superintendent of Tsukiji Hospital in Tokeyo, Japan, took upon the study of “skin-furrows”after noticing fingermarks on specimen of pottery. A learned and industrious man, Faulds not only recognized the importance of fingerprints as a mean of identification, but devised a method of identification as well. In the 1880’s, Faulds forwarded explanation of his classification system and a sample of forms he designed for recording ink impressions, to Sir Charles Darwin. Darwin, advanced in age, informed Faulds that he would not be any assistance, but he would pass on the information to his cousin, Francis Galton. Also in 1880, Faulds published an article in the Scientific Journal, “Nature.”He discussed fingerprints as a mean of personal identification, and used printer ink as a method of obtaining such prints.  Faulds was also credited with the first fingerprint identification of a greasy fingerprint on an alcohol bottle.

1882- Gilbert Thompson
In 1882, Gilbert Thompson of the U.S. Geological Survey in New Mexico, used his own fingerprint on a documnt to prevent forgery. This is the first known use of fingerprints in the United States.
    1888- Sir Francis Galton
Sir Francis Galton, a British anthropologist, and cousin of Charles Darwin, began his observations of fingerprints as a mean of identification in the 1880’s.

1891-Juan Vucetich
Juan Vecetich, Argentinian police officer, began the first fingerprint files based on Galton pattern types. At first, Vecetich included the Bertillon System with his files, but took it out.

Overall, fingerprints are very important in the identification of criminals and missing people. Society has come a long way with the discovery of fingerprinting.


Drury, Kristen Personal interview 10-13-05

Fingerprints 12-13-05

Heath, David Crime Lab Technician. Mankato, Minnesota: Capstone Press. all pgs.

Lampton, Christopher DNA Fingerprinting all pgs.

Merriam Websters. Dictionary.Springfield Massachusetts, USA, Merriam Websters inc., 1998. pg. 283.

Moore, Greg “The History of Fingerprinting” 11-7-05 

Owen, David Police Lab  11-12-05 all pgs.

Thornton, John “Fingerprinting” 10-14-05 World Book Online


I would like to thank the following people for helping make my project possible:
•    My parents for always being there for me and helping me whenever I asked.
•    Mr. Newkirk for always being ready to help me and knowing what to do whenever anything went wrong.
•    Mrs. Viernes for helping me find information and keeping me on task.
•    Kristen Drury of the Yakima Police Department for taking time out of her busy day to let me come down and get a better understanding of fingerprints.
•    All my friends for being ready to help even when they had other things they could be doing.

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