Murder Ink: Tattoos often used to symbolize wrongdoing, but rarely used as evidence of crime

FILE - This undated file photo provided by the Los Angeles Sheriff’s department shows convicted murderer Anthony Garcia, sentenced to 65 years in prison in 2011 after a homicide investigator discovered he had the scene of an unsolved 2004 murder inked on his chest. (AP Photo/Los Angeles County Sheriff's Department, File) (The Associated Press)

FILE - This undated file booking photo from the Kansas Department of Corrections shows Jeffrey Chapman, charged with first-degree murder in the November 2011 killing of Damon Galliart, whose body was found by in a ditch southwest of Great Bend, Kan. After his attorney claimed it would be prejudicial, Chapman will be allowed to wear a turtleneck to cover a tattoo on his neck of the word “murder” spelled backward when his trial begins in August 2014.(AP Photo/Kansas Department of Corrections, File) (The Associated Press)

Crime experts say it's unusual that investigators in the Aaron Hernandez murder cases have appealed for information from tattoo artists who inked the former New England Patriot star's right forearm.

Criminals have long marked their bodies with symbols of bad acts, including teardrops for murders, but experts say it's unusual when those tattoos become evidence of wrongdoing.

Criminal investigators hit the jackpot every once in a while with tattoos. Southern California gang member Anthony Garcia was sentenced to 65 years in prison for murder in 2011 after an investigator discovered Garcia had the murder scene tattooed on his chest.

Hernandez is accused of three murders in Massachusetts. His lawyers say he looks forward to proving his innocence.

Investigators won't say which of Hernandez's many tattoos prompted their appeal to artists.