Bio-identification systems can be divided into two main types: visual and electronic.
Visual bio-identification methods include use of photographs, signatures and/or finger or thumb prints on identity cards. These are relatively low cost to implement and administer. Many off-the-shelf identity card issuing systems incorporate inclusion of photographs and signatures. At polling places, polling staff are expected to compare the photographs, signatures and/or finger or thumb prints on the identity cards with the voters.
This process has its weaknesses, as signature and finger print comparison is a highly skilled process that polling staff can not be expected to master, and a person's appearance can often change significantly from that contained in an identity photograph, particularly if the photograph is not updated regularly. Nevertheless this kind of identity system will probably suffice in most cases where the risk of voting fraud is not unacceptably high.
If visual bio-identification systems are not considered secure enough, electronic bio-identification systems can be used. Electronic bio-identification systems can include digitised voice, hand print, finger/thumb print, or retinal (eye) images. Using these systems, digital records of a person's voice or physical features are stored on disk or smartcard and compared to the actual features of the person using some form of electronic reader. Access is only provided where there is an exact match.
Electronic bio-identification systems are expensive to acquire and administer, and may not be practical for use with the general voting population (although this may change as the relevant technology becomes more widespread and cheaper). However, they are a feasible option for providing security at sensitive locations such as work places and counting centres.