NEWARK, N.J. (CBSNewYork/AP) — A 20-year-old man has been convicted of murder and robbery in the execution-style slayings of three college-bound friends in a Newark schoolyard in 2007.

A jury found Alexander Alfaro, 20, guilty on 16 of the 17 counts.

Earlier Tuesday, controversy involving a female juror nearly caused a mistrial on the fourth day of deliberations.

Prosecutors said the woman didn’t acknowledge in a questionnaire before the trial started that she had a criminal case pending. Alfaro’s attorney moved for a mistrial, claiming the prosecution acted improperly by researching the juror’s background more than a month after jury selection.

The jurors reached the verdict less than an hour after a judge denied the motion.

newark schoolyard slayings Man Convicted Of Murder In Newark Schoolyard Slayings Trial

From left: Victims Terrence Aeriel, Ioefemi Hightower and Dashon Harvey

Dashon Harvey, Terrance Aeriel and Iofemi Hightower were shot execution-style behind Mount Vernon School, weeks before they were to attend Delaware State University.

The prosecution claims Alfaro played a part in the robbery that preceded the killings in Newark. Alfaro testified he watched the robbery but didn’t take part. He said he was coerced by his half-brother to bring a machete to the scene.

The jury began deliberating last Thursday after a four-week trial. On Monday, it was re-read testimony from a cousin of Alfaro’s who said he told her about the August 2007 attacks the following day. The woman had described how six suspects circled four friends and demanded that they lie on the ground and give up their valuables.

Six men and boys were charged. Two are serving multiple life sentences, and three more await trial.

Alfaro admitted in a taped statement that he slashed one of the victims with a machete before all three were shot execution-style, but said he was coerced into giving a false confession when he was arrested two weeks after the murders.

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