Face recognition is currently used to spot known hooligans at football matches. However, the process is difficult, time-consuming and prone to error. Once the suspect's image has been captured, it is necessary to compare it with many stored images. Depending on how the search criteria have been set, this could result in hundreds or even thousands of possible matches, which then need to be filtered according to other factors. Face-recognition specialist Neurodynamics says that its system is fast, accurate and allows for facial changes.
Faces can change with age, or through the appearance of blemishes and beards.
Similarly, fingerprint identification can be complicated by the presence of grease, dirt or earlier prints on the scanning device. In practice a biometric scan, sometimes called a live template, will rarely match the stored template exactly, and so a balance needs to be set between the level or false acceptances and the level of false rejections. A high level of false acceptance increases the risk of a security breach, while a high level of false rejections will increase support costs and annoy users. The balance will vary depending on the application. Palm prints, like faces, change gradually over time.