Rodolfo Godinez, a legal Nicaraguan immigrant who was one of six men and boys charged with the August 2007 slayings, was convicted on all 17 counts. A jury returned the verdict in state Superior Court after nearly four hours of deliberation.
Prosecutors sought to portray Godinez as a ranking member of the MS-13 street gang who orchestrated the killings of Dashon Harvey, Terrance Aeriel and Iofemi Hightower as a test for an aspiring member. The murders spurred a wave of anti-crime measures in Newark, from jump-starting a surveillance camera project to expanding access to gun-trace data.
A fourth victim survived the attack and testified against Godinez. She is not being identified by The Associated Press because of sexual assault charges against two other defendants.
All four victims were enrolled or about to be enrolled at Delaware State University.
Their family members wept and rubbed one another's backs quietly as the verdict was read. Earlier, when it was announced the jury had reached a verdict, several of them gasped and started clapping. The judge warned the gallery to stay calm once the verdict was read.
"For us to see him (Godinez) every day, coming into court with a simple smirk on his face, and to find out that we have the last laugh ... it's truly been a blessing and a healing process for us," Dashon Harvey's father, James Harvey, said following the verdict.
The surviving victim's father said he was extremely proud of his daughter for having had the strength to testify during the trial - adding that despite her ordeal, she had graduated college this past weekend.
Godinez's mother, who attended much of the trial, did not appear to be in the courtroom Monday.
Lawyer Roy Greenman, who represents Godinez, said he was disappointed with the jury's verdict and planned to appeal.
All six defendants are being tried separately.
Acting Essex County Prosecutor Robert Laurino said: "The verdict sends a message. We put forward our most difficult case, we won it."
Laurino added that prosecutors were "willing to go forward with the next five prosecutions, if necessary."
Without a wealth of physical evidence tying Godinez to the scene - he left DNA on a beer bottle at the playground but wasn't tied to the gun or knife used in the attacks - prosecutors used statements Godinez made to police and to a jailhouse acquaintance that appeared to implicate him.
The three slain victims were found slumped against a wall of the playground, each having suffered a gunshot wound to the back of the head. Hightower also was slashed with a machete.
The survivor testified last month, her first public account of what happened. She was 19 at the time of the attack and her identification of a picture of one of the suspects led to the capture of all six.
She said she and her three friends had gotten together to drive around and listen to music. While they were hanging out a playground, they were attacked by six men and boys. She described being sexually assaulted, slashed with a machete and shot in the head, but didn't identify Godinez as being present at the schoolyard.
Before deliberations, state Superior Court Judge Michael Ravin instructed jurors that, under New Jersey's accomplice-liability statute, they could find Godinez guilty of the murders even though there was no evidence presented that he pulled the trigger.
Greenman had argued his client was at the scene but didn't take part in the attacks.
Godinez will be sentenced July 8. The 26-year-old could spend the rest of his life in prison.
New Jersey Attorney General Paula Dow, who was the Essex County prosecutor at the time of the killings, called the verdict "just one of six pieces of a cold-blooded puzzle that shocked this city, this state, this nation three years ago."
The publicity surrounding the killings jump-started an effort to buy and install surveillance cameras and a gunshot-detection system in Newark's most dangerous neighborhoods.
State officials also gave police the authority to refer violent crime suspects' names to immigration authorities if they were suspected of being in the country illegally, a response to the fact that one of the suspects was free on bail for other crimes despite being an illegal immigrant.
Other changes followed, including the instituting of penalties for gun owners who fail to report lost or stolen weapons and a first-of-its-kind agreement to allow all New Jersey municipalities access to a federal gun-tracing database.
