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Biometric Systems

What are biometrics?

A biometric is a physical or behavioural feature or attribute that can be measured. It can be used as a means of proving that you are who you claim to be, or as a means of proving without revealing your identity that you have a certain right.

Biometrics which are commonly used to confirm identity include:

What is a biometric system?

A biometric system is essentially a pattern recognition system that operates by acquiring biometric data from an individual, extracting a feature set from the acquired data, and comparing this feature set against the template set in the database.

If you would like further background information on biometrics please click on the following link: An introduction to biometrics

Some physiological and medical factors can affect the usability and efficiency of biometrics:

Visually impaired

  • Aniridia, absence of iris, a phenomenon found in a proportion of 1.8 out of 100,000 births [1], which affects both eyes for genetic reasons [2]
  • Similar effects may be caused by laser iridotomy (used to correct angle-closure caused by glaucoma)
  • Blind people can have problems due to their natural difficulty to align their eyes with the camera
  • A similar case is that of people with pronounced nystagmus (tremor of the eyes)
  • People that have been operated on for cataracts may need to be re-enrolled, although empirical evidence suggests that relatively few people need to do so [3]

Hearing impaired

  • Speech may be affected due to loss of hearing resulting in difficulty in using voice recognition systems
  • Inability to hear instructions for example from the camera of face and iris recognition systems

Physically impaired

  • Conditions such as arthritis may affect usability (it may be difficult to position the finger and/or hand correctly)
  • Skin conditions such as eczema may cause blistering on the fingertips
  • Any kind of surgery that significantly changes the structure of the face, will require an individual to re-enrol
  • Cuts, bruises and swelling can have a temporary affect on face or hand images
  • Inability to use hand or finger based systems due to loss of limbs and or digits
  • Crutches may make it difficult to stand steadily
  • Drooping eyelids
  • Wheelchair users can face usability barriers due to the usual location of cameras and insufficient height variation possibilities
  • Changes in medical condition can be faster than normal ageing affects
  • Those with cerebral palsy, multiple sclerosis, muscular dystrophy, motor neurone disease etc, may have little control of their muscle movement and may find it very difficult to hold their head or fingers still long enough for a facial, iris or fingerprint recognition device. Similarly they may be unable to record a digital signature

Cognitively impaired

  • Dyslexia, language, learning or knowledge retention difficulties may make it difficult to reliably and consistently provide a biometric sample or otherwise navigate through an automated process

Language impaired

  • Speech and language disabilities include functional limitations in comprehension and expression, voice response rate, quality of voice and fluency, and stuttering which may affect using voice recogniton systems
  • Colds, laryngitis can have a temporary affect on the voice

Older people

  • Biometrics usually have higher failure rates with the very old. As people get older, ageing processes tend to degrade biometrics. For instance the ridges of their fingerprints wear down and cataracts are more prevalent.
  • In addition to visual impairments, many older people have a combination of impairments (cognitive impairments such as dementia, physical impairments such as arthritis and Parkinson's disease etc). Also multi-tasking becomes less easy. The effect of all these factors is that many older people may have problems in using a biometric terminal at the same speed as their younger counterparts if at all

Accessibility problems for non-disabled people
Accessibility problems may not be restricted to disabled people. Other groups of people maybe affected, for example, people carrying out construction and manual work. People working with cement and chemicals may result in the wearing down of fingerprints.

The wearing of veils due to religious reasons may result in some people being unwilling to use certain biometric technologies such as face and iris recognition systems.

Poeple who have had cosmetic surgery (eg. botox) may have problems with face recognition systems, in particular at the authentication stage if they have had the procedure after the enrolment stage.

Cold weather may affect people using fingerprint and signature recognition systems especially if the authentication terminals are outside.

If the instructions of how to use an unmanned enrolment or authentication terminal are not clear then this will affect everbody in using all systems.

Advantages of biometrics for people with disabilities
The obvious advantage of biometric systems is that the user no longer has to remember PINs (personal identification numbers) and keep this number secret. People with a cognitive impairment will find most biometric systems much easier to use and provide a greater level of security.

People who have limited or no use at all of arms or hands will find using face and iris recognition systems an advantage as they will not have to swipe a card or type in a name or PIN number.

Enrolment Terminals
To register a biometric for public use (eg. for a passport), the subject will usually have to go to a centre where specialist staff take the biometric and check other relevant documentation. Ideally these staff should be trained to work with people with disabilities. For private use (eg replacement for a password on a personal device such as a laptop computer), the subject is expected to follow instructions on the screen or in a printed manual to register the biometric.

The environment of the enrolment centre needs to meet the general accessibility for public access terminals. However specific biometrics will require special consideration (see details in the sections related to the various biometrics).

Authentication Terminals
These may be fully supervised, partially supervised or un-supervised; this is likely to be significant for occasional users and for some people with disabilities. In general, a consistent user interface will benefit all users and may be of particular importance for some people with disabilities. With un-supervised terminals it would be beneficial for there to be a standardised set of icons, symbols and pictograms for the operation of the terminal.

It is essential that the authentication terminal is comfortable to use. For instance, enrolment of fingerprints will normally be done with the subject sitting down. However the authentication may be done with subject standing. It is important that the height and angle of the fingerprint reader is comfortable for both a tall person and someone in a wheelchair. If it is not viable to make the reader variable height (or on a flexile lead), it might be helpful if it was tiltable to allow a comfortable angle for the wrist. A wrist rest might be beneficial for a subject with hand tremor.

Like all input devices on public terminals, it is important that the device gives both auditory and visual feedback of the current status (eg still processing, accepted, rejected). It is also important that error messages are helpful and give guidance on what the subject should do differently.

Ability to update biometric
The biometric information can be stored in a central database or on a smart card. Users are likely to prefer the information to be stored on their card rather than on a remote database. However, it is easier to regularly update the database with revised biometric data as the user's characteristics change.

Using multimodality to enhance the usability of systems

Two (or more) modalities could be combined in parallel to produce a system that would allow more flexible use. For example biometric systems built for both fingerprint and face recognition, could allow the use of only the facial image for verification when users have problems enrolling their fingerprints and vice-versa. Moreover, this procedure could prove extremely useful to those users who have temporarily lost the ability to provide one of their biometric traits (for example, a temporary eye problem that rules out an iris scan). The same could apply in cases where people refuse to use a specific modality (for religious or health purposes, for instance). A multimodal system therefore allows enhanced flexibility by providing alternatives for the identification process. As such, it also has the potential to be more socially inclusive.

Section 5.4.38 Biometric Characteristics of the draft European standard EN 1332-4 Identification Card Systems - Man-Machine Interface - Part 4: Coding of user requirements for people with special needs relates to a multimodal tag.


General Recommendations

Providing instructions in an accessible format

For example, if an iris scan is not successful: "This scan was not successful, please turn your head slightly to the right."


if a fingerprint scan is not successful: "This scan was not successful, please hold your finger still on the reader."

Informing the user that the reader is waiting for him/her to take action

Catering for users who do not require audio instructions (e.g. those who have good vision, or those who are familiar with the process)

Reference: Identification of Accessibility Issues for Visually Impaired Users of Biometric Technologies: Fingerprint Readers


A draft ISO standard is under development that will highlight the needs of the disabled and suggest practical ways of addressing their needs:

  1. Systems using a biometric should be designed so that as many potential subjects as is reasonably possible can use the system effectively and with the minimum of discomfort.
  2. In the design of such new systems or services, the needs of disabled subjects should be considered from the outset.
  3. Before systems are deployed, they should be thoroughly tested with subjects who represent the widest range of abilities (that is, in respect of visual, auditory, physical, cognitive and behavioural ability).
  4. For subjects with a disability, adequate training in the use of the system should be offered.
  5. Wherever practicable, the subject should have a choice of biometric systems, and should not be discriminated against if their disability prevents them from using a specific biometric.
  6. Where no alternative biometric is available and where the disability prevents the use of this biometric, subjects should be permitted to use an alternative method. Wherever practicable, the use of such an alternative should not result in an inferior level of service or functionality to the subject.
  7. If the subject can no longer use a verification system reliably, the subject should be provided wherever feasible with the opportunity to repeat the registration process.
  8. Staff operating systems using a system with biometrics should be trained in how to process disabled subjects.
  9. A system using a biometric should not store details of a subject's disabilities without their informed consent.
  10. The rights of privacy of a disabled subject should be the same as those of a non-disabled subject.


In the United States of America, the Biometric Standards, Performance and Assurance Laboratory of Purdue University, focuses on the data collection of "extreme populations". An examples are the elderly and those that have illnesses that can affect a biometric either through the illness of the treatment is Image quality and the elderly: an initial study examined how fingerprint image quality was affected by age.


The Biometric Foundation is dedicated to a systematic program of research and education to reduce impediments to wide adoption and use of all biometric technologies. The Foundation will address technical, societal, and legal aspects of biometric technologies and their applications. Accordingly, the Foundation's agenda will include studies of public attitudes toward uses of biometrics; demonstration and evaluation of alternative biometric technologies; inquiry into biometric standards issues; development of formal educational curricula that encourage students to enter the field of biometrics as a professional career choice; and conferences and seminars about the most effective uses of biometrics in key applications.

UK Passport Service (UKPS) Biometrics Enrolment Trial (PDF)
The goal of the UKPS Biometrics Enrolment Trial was to test the processes and record customer experience and attitude during the recording and verification of facial, iris and fingerprint biometrics, rather than test or develop the biometric technology itself. One of the 3 sample groups recruited were a disabled participant sample of 750.

According to the UKPS, the trial results highlighted several issues that require further investigation or work. Among other things, further trials are needed, specifically targeted towards those disabled groups that have experienced enrolment difficulties due to environment design, biometric device design, or to specific group problems - for example, black participants and participants aged over 59 had lower iris enrolment success rates.

Further information

[1] US National Eye Institute
[2] Royal National Institute of the Blind
[3] “Iris recognition as a biometric method after cataract surgery” Roizenblatt et al


The information contained in this section was collected from the following sources:


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