One of the most long-lived and effective biometric methods, fingerprint identification has been employed for over 100 years. In all of that time, nobody has found two sets that are identical, not even with identical twins. Though the practice itself has existed for decades, the ways in people collect and record fingerprints has changed drastically. Rather than dusting for prints or using paper and ink to record fingerprints, computers now do most of the heavy work, scanning fingerprints into databases and networks. Beyond security and detective work, this biometric method has even been employed commercially, even used to help prevent vehicle theft.
As with fingerprints, every person's face is also unique.Because a usable image of somebody's face can be taken in an instant with a camera that is very far away, this method of biometrics could become quite effective in fighting crime. There are two different methods of facial recognition currently employed. The first, known as facial metrics, analyzes and records the numerical difference between different points common to every person's face, such as the distance between the insides of a person's eyes or the distance of the nose to the mouth. Combining all of these measurements together, facial metrics can create a unique numerical code representative of a person's face that is unique to that individual. The second method is called eigenfaces and uses pieces of 150 set face shapes to reconstruct an individual's face with 99 percent accuracy.
Two major biometric methods have evolved based on an individual's eyes. Both the iris (the colored part of the eye) and the retina (the back part of the eye) are unique for every individual, and scanning equipment and programs have developed that identify people using each part of the eye. This type of biometry is typically only used for identification at secure facilities, such as government or military buildings, because it is quite invasive to the subject. It is nearly impossible to acquire without the subjects consent. It is also less certain than something like a fingerprint, particularly because eye conditions such as cataracts can change the characteristics of the subject's eye, rendering the scan useless and ineffective.
Each person's voice is also unique, and certain software and computer programs have developed that can analyze a person's voice and can make a unique print of it. Still, the software often must have multiple phrases before the technology can create an accurate profile of a subject's voice, and even then, accuracy can be limited. So, like eye scans, this method of biometrics is usually employed for added security rather than for criminal identification.