Describe tattoo marks and their medicolegal importance.

Definition and Method

• Common pigments — Indian ink and carbon (black or blue-black), cinnabar or mercuric sulphide (red), cobalt (blue), chromium (green) and cadmium (yellow). Modern professional inks are organic dyes
• Fate of the pigment — it is engulfed by dermal macrophages and remains largely fixed, but some is carried by lymphatics to the regional lymph nodes, which may be pigmented and is a finding at autopsy that can indicate a removed tattoo
• Persistence — a tattoo persists after death and through putrefaction, often remaining legible when the skin is otherwise unrecognisable; wiping the decomposed epidermis away or examining the undersurface of the reflected skin may reveal a tattoo that is invisible from outside — a technique of real practical value in a decomposed unknown body

Medicolegal Importance

• Identification — the principal value. Tattoos frequently give the person's name, the name of a relative or partner, a date, a regimental or unit number, a religious symbol or a deity, and these may identify an unknown body directly
• They indicate a great deal about the person — religion and community (a trident, a cross, a religious inscription); region, since designs are strongly regional in India; occupation (naval, military and merchant marine designs); social group, gang or prison affiliation; and, sometimes, a criminal history
• The site is informative — exposed sites in decorative tattooing, and concealed sites where the design is intended to be private
• Age of the tattoo — a recent tattoo is raised, red and inflamed with scabbing; over months the colours become duller and the outline blurred as pigment is dispersed and removed. Only a broad estimate is possible
• Complications, which may themselves have medicolegal consequences — local sepsis, cellulitis and tetanus; transmission of hepatitis B, hepatitis C, HIV and syphilis from shared needles; allergic and granulomatous reactions, particularly to red mercuric pigment; keloid formation; and rarely malignant change in a scar

Removal and Applied Aspects

• Deliberate removal — by excision and grafting, dermabrasion, chemical destruction with acids or caustics, electrolysis, or Q-switched laser, which is the modern method and works by fragmenting the pigment for removal by macrophages
• Removal leaves evidence — a scar whose shape often reproduces the outline of the design; residual pigment at the margins or in the deeper dermis; and pigment IN the regional lymph nodes, which persists indefinitely and may be the only remaining proof that a tattoo existed. A person who removes a tattoo to avoid identification therefore leaves a mark that is itself identifying
• Examine the whole body surface in every unidentified case, including the scalp, the axillae, the perineum and the soles, and photograph every tattoo in colour with a scale
• Look at the undersurface of the skin in decomposition where a tattoo is suspected but the epidermis has been lost; the pigment is in the dermis and remains
• Examine and record the regional lymph nodes where a suspicious scar suggests a removed tattoo; pigmented nodes are strong corroboration
• Do not rely on a tattoo alone to establish identity; it is corroborative and directive rather than conclusive, since designs are shared and names tattooed are frequently not the wearer's own
• Advise about the infective risk; unsterile tattooing remains a genuine route of hepatitis B and C transmission in India, and is a recognised deferral criterion for blood donation
• A tattoo indicates region, community and often occupation, which may direct an investigation even where the design carries no name
• Date a tattoo only broadly — recent ones are raised and inflamed, and old ones are dull and blurred; a closer estimate cannot be defended
• Photograph in colour with a scale and record the exact site measured from a bony landmark; a description without a photograph loses most of the detail
• A tattooed name is frequently not the wearer’s own, but that of a partner, parent or deity — a point that has misdirected identifications
• Consider the tattoo when a scar of odd shape is found; a curved or geometric scar in a common tattoo site with pigmented regional nodes indicates a deliberately removed design
• Red mercuric pigment causes granulomatous reactions, which may present as a swelling in an old tattoo and be mistaken for something more sinister