Perea was also convicted of two counts of first-degree felony attempted murder for wounding two others during the gang-related drive-by shooting.
Second District Judge Ernie Jones handed down a sentence of life without the possibility of parole, rather than a less harsh prison term of 25 years to life.
Perea who was 20 years old at the time confessed to police that he was the one who leaned out of the front passenger-side window of an SUV and fired over the roof of the car into the wedding party, but during Perea's 2010 trial, defense attorney Randy Richards argued that Perea was ordered by an older gang member to "take the rap" for the shooting, and that Perea confessed to protect his family.
Newton argued Wednesday that Jones erred by not allowing a defense expert to testify about why people falsely confess to a crime they did not commit.
But Assistant Attorney General Christopher Ballard argued that the expert was "unhelpful" and "unreliable" and that a jury didn't need an expert to understand that a person could lie or falsely confess to protect their family.
Newton also argued that Jones ruled prior to the trial that a computer-animated reenactment prepared for the defense could be used at trial, but in the middle of the trial Weber County prosecutors raised an issue with the reenactment and Jones changed his mind.
This was unfair, Newton argued, because prosecutors were able to show a reenactment of their version of events, but the defense was not allowed to show a reenactment of their theory of the case.
At trial, Richards claimed "two, three or maybe four guns were used" during the attack, and none of them was fired by his client.
Ballard argued that Perea's attorneys were confused, and that Jones never ruled about the reenactment specifically before trial. He said the defense video was not shown to the jury because of issues with the reenactment, including questions about who created it and because it contained factual errors such as an incorrect bullet trajectory and use of the wrong type of vehicle.
But several of Supreme Court justices wondered why the defense computer reenactment could not have be shown, followed by prosecutors arguing those issues during cross-examination.
"I have to admit, I am mystified by your argument," Justice Christine Durham told Ballard.
Newton also argued that Utah's life without parole statute is unconstitutional because it gives no guidance to judges regarding sentencing.
The Supreme Court took the matter under advisement Wednesday. A decision will likely be months away.