Timberlake played a fictional character called Frankie Ballenbacher
Drug dealer Jesse James Hollywood, whose crimes inspired the 2007 film Alpha Dog, starring Justin Timberlake, has been found guilty of murder.
The 29-year-old was convicted of kidnapping and killing teenager Nicholas Markowitz, 15, in August 2000 over debts owed by his half-brother.
Hollywood fled after the slaying and was captured in Brazil in 2005.
Four others have already been convicted in connection with the crime. Hollywood could now face the death penalty.
Markowitz was the brother of a small-time drug dealer Ben Markowitz. During trial, it emerged that he had been killed following a dispute between his brother and Hollywood over more than $2,000 worth of marijuana.
The 15-year-old was held hostage for several days, before being bound with duct tape, struck over the head with a shovel and shot several times.
After four days deliberation, a Santa Barbara Superior Court jury also found Hollywood guilty of the special circumstance allegation of being a principal in a murder committed in the course of a kidnapping and being involved in a crime in which an assault weapon or machine gun was used.
The guilty conviction makes Hollywood eligible for the death penalty.
Taking the stand in his own defence, Hollywood said: "I just feel terrible about everything that happened. I feel terrible for the Markowitz family.
"I feel terrible that anyone would think I could do something like that."
The crime was the inspiration for Alpha Dog, which starred Bruce Willis, Justin Timberlake, and Sharon Stone.
Timberlake's character, Frankie Ballenbacher, was based on Jesse Rugge, one of Hollywood's co-defendants, currently serving a life sentence.
Emile Hirsch played Johnny Truelove, a character based on Hollywood.
The sentencing phase of the trial begins on Monday.