Tattoos are used among criminals to show gang membership and record the wearer's personal history—such as his or her skills, specialties, accomplishments and convictions. They are also used as a means of personal expression. Certain designs have developed recognized coded meanings. The code systems can be quite complex and because of the nature of what they encode, the tattoos are not widely recognized.

Australia

Prisoners who were transported from Britain to Australian penal colonies between 1787 and 1867 were sometimes tattooed with marks intended to signify disgrace, for example D for deserter. However, prisoners often modified these tattoos to conceal the original design or to express wry or rebellious messages.

North America

Common tattoos are names of relatives or gang members, symbols of aggression (such as skulls), tattoos advertising a particular skill, or (among Latino prisoners) religious imagery.

Russia

Russian criminal tattoos have a complex system of symbols which can give quite detailed information about the wearer. Not only do the symbols carry meaning but the area of the body on which they are placed may be meaningful too. The initiation tattoo of a new gang member is usually placed on the chest and may incorporate a rose. A rose on the chest is also used within the Russian Mafia. Wearing false or unearned tattoos is punishable by death in the criminal underworld. Tattoos can be voluntarily removed (for loss of rank, new affiliation, "life style" change, etc.) by bandaging magnesium powder onto the surface of the skin, which dissolves the skin bearing the marks with painful caustic burns. This powder is gained by filing "light alloy" e.g. lawnmower casing, and is a jailhouse commodity.

Tattoos done in a Russian prison have a distinct bluish color and usually appear somewhat blurred because of the lack of instruments to draw fine lines. The ink is often created from burning the heel of a shoe and mixing the soot with urine, and injected into the skin utilizing a sharpened guitar string attached to an electric shaver.

In addition to voluntary tattooing, tattoos are used to stigmatize and punish individuals within the criminal society. They may be placed on an individual who fails to pay debts in card games, or otherwise breaks the criminal code, and often have very blatant sexual images, embarrassing the wearer. The victim of a forcibly applied tattoo is nevertheless required to pay the tattoo artist for his work.

Tattoos on the forehead are usually forcibly applied, and designed both to humiliate the bearer and warn others about him or her. They frequently consist of slurs about the bearer's ethnicity, sexual orientation, or perceived collusion with the prison authorities. They can indicate that the bearer is a member of a political group considered offensive by other prisoners (e.g. Vlasovite), or has been convicted of a crime (such as child rape) which is disapproved of by other criminals.

Tattoos that consist of political or anti-authoritarian statements are known as "grins". They are often tattooed on the stomach of a thief in law, as a means of acquiring status in the criminal community. A Russian criminologist, Yuri Dubyagin, has claimed that, during the Soviet era, there existed "secret orders" that an anti-government tattoo must be "destroyed surgically", and that this procedure was usually fatal. Consequently, such tattoos were also sometimes applied forcibly to the back of a violator of the "thieves" code', as punishment.

The four suits

• Spades – the "suit of thieves"
• Clubs – a "criminal" suit that represents a sword (mostly ex-warriors)
• Diamonds – the "chummy suit" (i.e. stool pigeons and informers). This suit is usually forcibly applied.
• Hearts – a sexual symbol. It marks the wearer out as a "passive homosexual"/sex object within the prison/sex toy.

Egyptian tattoos

• Eye of Horus – Protection from enemies/back-stabbers
• Anubis – Protection from death
• Ankh – Eternal life
• Spades – The Prince of thieves