Prosecutors unveiled a smoking gun Thursday in the case of four Santa Rosa gang members charged with the mistaken identity killing of Vallejo musician Dewey Tucker.

And it was tattooed on one of the defendant's shoulders.

Photographs of Raul Vega, 20, the suspected shooter in Tucker's 2010 freeway slaying, show him sporting an ink etching of a masked gunman holding a smoking pistol.

When it was discovered by police at his arrest last year alongside other tattoos of people with guns, Vega admitted he got it for killing Tucker.

"He said to police it was earned for the homicide of Dewey Tucker," testified Officer Shawn Harvey, a special gang detective for the California Highway Patrol.

The revelation came during trial testimony for one of Vega's co-defendants, Christopher "Spider" Mancinas, 31.

Mancinas is the first to face a jury on murder charges. The rest — Hector Barragan, 31, Javier Carreon-Lopez, 21, and Vega — will be tried later this year.

Prosecutor Bob Waner illustrated how gang tattoos can be a roadmap for detectives. He showed a series of photos of the four defendants, stripped to the waist, exposing sometimes elaborate body art.

All had markings announcing their allegiance to the sure? gang. Mancinas had "sure?" scribbled across his forehead and "sur" in big letters on his abdomen.

Barragan had life-sized semi-automatic pistols on each hip, as if they were tucked into a waistband. A cracked Northern Star, the symbol for rival norte?s, was on a shoulder.

Carreon-Lopez had the numbers one and three on opposing shoulders, forming a 13, which is a symbol for the sure? gang.

Vega, who goes by the moniker "Crime" or "Crime Time," had at least three depictions of guns — all believed to be connected to past violent acts.

The most incriminating was the masked gunman, which he obtained sometime after Tucker was shot to death on Jan. 12, 2010, as he drove on Interstate 80 to a music rehearsal.

Prosecutors said the four defendants mistook him for a gang rival who lived in a nearby apartment.

Vega's other tattoos include a picture of the Grim Reaper, which the detective testified shows his willingness to kill for his gang.

"It's an indication of death and pointing out at the audience," Harvey said.

Vega is charged with murder in a separate killing on the campus of Kawana Springs Elementary School in Santa Rosa in January 2011.