Human fingerprints have been formed since the fetus was four months old, and have become one of the basic physiological and physical characteristics of each person. Fingerprint characteristics are quite fixed and will not change as a person ages or changes in physical health, and each person's fingerprints are different. The Henry system, which is the basic theory of fingerprint identification technology, states that each fingerprint generally has 70-150 basic feature points. From a probabilistic perspective, two fingerprints can be identified as the same fingerprint as long as 12-13 feature points match. It takes 120 years for two identical fingerprints to appear.

The probability that two people have the same fingerprints is so small that it is almost zero. Only in 1000 trillion people can there be two people with exactly the same fingerprints. So we have every reason to say that just as there are no two identical snowflakes, there are no two people with the same fingerprints in the world. Therefore, if the police find a fingerprint left by a criminal at a crime scene, and it matches the fingerprint in a fingerprint file, the criminal's identity can be determined immediately.

Fingerprints have been used to identify and determine people’s identities for a long time. Hundreds of years ago, the Chinese used thumbprints to sign documents or contracts, which may be safer than a signature because it cannot be forged. But the first person to use fingerprints to systematically identify people was Englishman William Herschel around 1850, when he was a British government official in India. Hershel was troubled by the fact that Indians often pretended to be each other's names, so he came up with the idea of ??using fingerprints to identify everyone. His measures worked immediately, and no one could fish in troubled waters and hide their identity anymore.