A tattoo is a design imprinted onto the skin that can sometimes be a useful mark of identification of a non-skeletalized body or a suspect using a false identity. It is believed that tattooing was first practiced in Egypt around 2000 b.c., and its use has spread around the world. Today a wide cross section of the population bears tattoos, from fashion models to known criminals and gang members. The designs are as varied as the people who wear them; names of loved ones are popular, as are symbols denoting membership of a group. Tattoos may be done just for fun, or they may have a more sinister connotation; for instance, prisoners have sometimes been tattooed with numbers, especially in concentration camps. Some elderly people may bear tattoos relating to experience in the Holocaust.
When a pathologist carries out an autopsy , he or she will look for and record tattoos in the same way as for any other body marks that could be identifying, like scars or birthmarks. The location and nature of the tattoo are the identifying features. A tattoo is made by inserting dyes or inks into piercings created by a needle. One approach to identifying the body is to extract a tiny amount of the dye and subject it to laboratory analysis. The pigments can be identified by techniques such as atomic absorption spectroscopy or thin layer chromatography and may be traceable back to a specific tattoo artist. Black pigments may contain carbon, reds mercuric chloride, and greens potassium dichromate.
Tattoos are valuable identification marks because they tend to be permanent. They can be removed, but they do not fade, and they persist even if the outer layer of skin has perished. The color may, however, change with exposure to the sun. Typically, blue pigment may turn black or purple.
When it comes to identifying a corpse, family members may be aware of the existence of a tattoo and this can be used as a distinguishing mark even if the body itself has been dismembered or otherwise mutilated. In one famous case, dating back from 1935, two fishermen caught a shark off the coast of Sydney, Australia, and took it to a local aquarium where the animal proceeded to disgorge a human arm. The limb appeared to have been severed by a knife, seeming to rule out a shark attack as the cause of death . It looked, rather, as if the corpse had been dismembered and disposed of at sea. The arm also bore a distinctive tattoo of two boxers squaring up for a fight. This led to the identification of the victim as James Smith, an ex-boxer with a criminal past. His wife recognized the tattoo, and fingerprint evidence confirmed the identity. Suspects were arrested, but the defense argued that an arm alone was insufficient evidence to convict, even if it did carry a tattoo and fingerprints. The case became known as the Shark Arm Murder.
Statistics show that people with anti-social personality disorder are often involved in crime, and they are also more likely to bear a tattoo than the rest of the population. The reason for this is unknown, but the tattoo can be a useful way of identifying these people. Indeed, this may be why criminals on parole sometimes can be identified through their tattoos if they run into more trouble. Often an ex-convict will have a tattoo bearing his name, his street name, or the name of a loved one. If he carries a gun, he may reveal this through a tattoo of the weapon. Wearing a tattoo may be a part of gang and criminal culture. For some people, the tattoo is an important part of belonging and of intimidating others. Certain gangs have distinctive tattoos. In California, the CALGANG database stores data on gang tattoos. This is a useful resource for the investigator who finds a tattoo on a corpse suspected of being the victim of a gangland killing or similar incident.
In Florida, a database has recently been created which includes around 372,000 tattoo records. All of these have been found on examination of criminals serving sentences in the state's prisons. Any investigator discovering a tattoo on a suspect or body can now utilize this database to try to find an identifying match. On its own, a tattoo may be insufficient evidence of identity, but it can be crucial when placed in the context of the whole investigation.
see also Identification; Profiling.