Forensic implications of fingerprint verification failure among people with skin diseases

Conditions causing histopathological changes of the epidermis and dermis

Conditions under this category can potentially affect fingerprint recognition due to their alteration of epidermal and dermal structure as well as skin colour. ⁷

Eczema is a relapsing long-lasting inflammatory condition characterised by acute episodes of pruritis, erythema and vesiculations. It is often caused by exposure to irritant or toxic substances such as chemicals. Repeated additive exposure to such substances causes disruption of the skin barrier and the development of secondary features such as hyperkeratosis and lichenification. ⁹ Fingertip eczema, in particular, is characterized by dryness and peeling of the fingertips distally, often revealing a red, tender and fissured palmar surface without skin lines. ⁷

Pompholyx or dyshidrotic eczema is a distinctive type of eczema, distinguished by the sudden onset of many deep-seated clear pruritic vesicles. With time, the vesicles slowly regress leaving behind scaly rings that may be accompanied by chronic eczematous changes such as lichenification. ⁷

Tinea manuum is an often-unilateral fungal infection of the hands. It is characterized by well-demarcated scaling patches, hyperkeratosis and fissures on the palms of the hands. ⁹

Pyogenic granuloma is an acquired, rapidly growing vascular abnormality that is mostly due to hormonal influences or minor trauma. Lesions appear as a bright red to yellowish papule or nodule, frequently on the fingers, toes, lips and trunk. It has a tendency to bleed either spontaneously or after trauma and develop into a crusty papule. ⁹

Scleroderma is an autoimmune disease commonly affecting females of age 30–50 years. The aetiology is unknown; however, endothelial injury might be a precipitating factor leading to oedema followed by fibrosis. Limited systemic scleroderma, in particular, causes fingers to appear oedematous and curved downward with characteristic acrosclerosis, a combination of Raynaud’s phenomenon and tightening/thickening of the skin. The thickened skin can become ulcerated and necrotic, typically referred to as “rat bite” necrosis. ⁷

Raynaud’s phenomenon is an ischaemic episode of the fingers due to underlying vasoconstriction of the digital vessels. It can be primary without an underlying cause or secondary to underlying conditions such as connective tissue diseases and obstructive arterial diseases. The phenomenon is often triggered by emotional stress or exposure to cold. During the episode, the fingers initially become pale reflecting the underperfusion of the digits, cyanosed representing the slow reperfusion after re-warming and then red or hyperaemic representing the reactive hyperaemic phase after restoration of blood flow. In cases when the episode becomes persistent or upon repeated attacks, the skin becomes atrophied, ulcerated and eventually gangrenous. ⁷

Erythema multiforme is a cutaneous manifestation of multiple possible aetiologies. It is more common among males. It can be secondary to infections, predominantly herpes simplex virus, or medications such as sulphonamide, phenytoin and barbiturates. It appears as a target-shaped erythematous lesion with a central blister or crust. It can be localised to the hands and face or generalised. ⁹

Conditions causing skin discolouration

Conditions under this category may hinder adequate fingerprint recognition, particularly by means of optic sensors, due to their alteration of skin pigmentation. ⁷

Hand, foot and mouth disease is a symmetric viral infection of the skin, commonly caused by the coxsackievirus A16. More commonly seen in children, it is a self-limiting disease that is characterised by red macules and papules that quickly evolve into vesicles on the palms and soles, especially on the sides of fingers, toes and buttocks. ⁹

Xanthomas are cutaneous yellow-brown, pinkish or orange macules, papules, plaques, nodules or infiltrations of fat in the skin and tendons. These deposits are usually localised to the palmar creases and fingers. They typically occur in the context of underlying lipid disorders. ⁷

Scarlet fever is a complication following group A β-haemolytic streptococcal infection that commonly affects children. The characteristic rash consists of many small spots or punctate lesions that fade within 4–5 days followed by desquamation of the body with sheet-like exfoliation of the hands and feet. ⁹

Kawasaki disease is an acute multisystemic vasculitis of an unknown aetiology commonly affecting children, predominantly males. Cutaneous involvement includes an erythematous rash associated with oedematous hands and feet. The affected area ultimately undergoes desquamation, typically beginning at the tips of the fingers. ⁷

Hereditary haemorrhagic telangiectasia is an autosomal dominant vascular disease. It is characterised by erythematous macular and pulsatile telangiectases found on the lips, tongue, conjunctiva, palms, fingers, soles and throughout the gastrointestinal tract. ⁹

Diseases causing histopathological changes at the epidermis–dermis junction

Conditions under this category may alter fingerprint recognition, especially by ultrasonic sensors, due to their alternation in the base of the papillary lines at the epidermis–dermis junction. ⁷

Verruca vulgaris or the “common wart” is a viral cutaneous disorder caused by the contraction of human papilloma virus. It is recognised by its firm hyperkeratotic papules with red or brown dots. Eruptions typically occur at sites of trauma, like the hands and fingers. Palmar lesions typically distort the normal line of fingerprints; hence, the return of fingerprints is a sign of wart resolution. ⁷

Psoriasis is a chronic disorder triggered by stress, trauma and drugs in genetically predisposed individuals. It is characterised by relapsing and remitting episodes of scaly papules and plaques. At times, palms and soles may be the only areas involved. In such cases, massive silvery white or yellowish hyperkeratotic well-demarcated plaques are seen, often accompanied with cracking, painful fissures and bleeding. ⁹

Epidermolysis bullosa is a term given to a group of inherited diseases that are characterised by bullous formation following minor trauma or friction. In some variants of the disease, blisters heal without scarring while in other cases blisters may heal with atrophic scarring resulting in syndactyly, loss of the fingernails and a mitten-like deformity of the hand.^7,9

Hand-foot syndrome is a dermatological reaction to certain chemotherapeutic agents. It initially begins with paraesthesia of the palms and soles followed by painful erythema. It is characterised by dermal changes, including blood vessel dilation and papillary oedema. ¹⁰