NEWARK, N.J. (CBSNewYork/AP) — School security procedures were the focus Tuesday, as a civil trial resumed in connection with the 2007 execution-style schoolyard killings that left three college-bound friends dead.

Iofemi Hightower, Dashon Harvey and Terrance Aeriel were shot behind Newark’s Mount Vernon School on Aug. 4, 2007. Six men and boys arrested for the murders have pleaded guilty or been convicted and are serving combined sentences of more than 1,000 years.

The suit, brought by the families of the victims and a fourth victim who survived the attack, claims the Mount Vernon School was negligent by leaving the playground open at night when it was a known gang hangout.

According to the lawsuit, the school’s security cameras did not work and the playground was poorly lit.

The civil trial entered its second week on Tuesday. A school district security supervisor, the school’s principal and two security guards testified on security procedures at the schoolyard.

The Star-Ledger of Newark reported the principal and district supervisor testified the gates were to be locked after 6 p.m. by security guards.

One of the guards testified there wasn’t a blanket policy regarding gates but that it was up to individual schools.

Charles Owuzuruike told jurors that if he found gates open, he would go in and check the school’s exterior. Owuzuruike exited the schoolyard through the open gates about two hours before the murders occurred.

The three victims and a fourth friend who survived being shot and stabbed were high school friends from Newark who played in marching bands and were enrolled or about to enroll at Delaware State University.

In an earlier criminal trial for one of the defendants, the lone survivor testified that she was sexually assaulted, slashed with a machete and shot in the head.

The survivor has testified in criminal trials that the four drove into the schoolyard and parked near some bleachers, where they listened to music and drank sodas. They were then set upon by six men and boys who robbed them, then forced three of them to walk down a set of stairs and kneel against a wall, where they were each shot in the head.

All six defendants pleaded guilty or were convicted by juries. Five are serving multiple consecutive life sentences, while a sixth received a 30-year sentence in exchange for testifying for the prosecution.

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