(CNN) -- An Arizona jury Wednesday found Jodi Arias guilty of first-degree murder for killing Travis Alexander in June 2008. The conviction means Arias could face the death penalty. In the next phase of the case, prosecutors will have a chance to present additional evidence and jurors will decide whether Alexander's death was caused in a cruel manner.

Since Friday, jurors have been deliberating evidence surrounding this key question: Did Arias kill ex-boyfriend Travis Alexander in self-defense? Or did she commit murder?

Alexander was stabbed repeatedly, shot and nearly decapitated five years ago. Arias says she killed him in self-defense after he attacked her, but the grisly slaying has caused even some anti-domestic violence advocates to doubt her case.

The jury, which has been in court since January 2, heard closing arguments on Friday. Jurors deliberated for 15 hours and five minutes.

As they took a lunch break after revealing they had reached a verdict Wednesday, some jurors were seen smiling and breathing sighs of relief. One juror returning from lunch wiped her eyes.

A massive crowd swarmed around the Maricopa County Courthouse Wednesday afternoon as word spread that a verdict had been reached. Some onlookers said they had been following the trial for months.

"We are here every day to support Travis' family 100%," said Kathy Brown, who got a cane she uses autographed by prosecutor Juan Martinez. "It's emotional, because I really feel in my heart that there's going to be a first-degree murder conviction."

If the jury convicts Arias of first-degree murder, jurors then will have to decide whether she lives or dies.

The trial began as both sides dramatically presented their arguments with details about Arias' love affair with Alexander.

"She rewarded that love from Travis Alexander by sticking a knife in his chest," Martinez said in his opening statement. "And you know he was a good man, according to her. And with regard to being a good man, well, she slit his throat as a reward for being a good man. And in terms of these blessings, well, she knocked the blessings out of him by putting a bullet in his head."

But defense attorney Jennifer Willmott countered: "Jodi Arias killed Travis Alexander. There is no question about it. The million-dollar question is what would have forced her to do it?"

Martinez accused Arias of playing the victim. He alleged she staged the crime scene to make it look like self-defense.

He also accused her of actively seeking to profit from her media attention.

Willmott said Arias was the victim of a controlling, psychologically abusive relationship, and Alexander considered Arias "his dirty little secret."

The prosecution pushed for a first-degree murder conviction. If convicted on this charge, Arias would face a mini-trial of sorts to determine whether she killed Alexander cruelly and knew he would suffer.

A first-degree murder conviction also could result in Arias' execution unless a jury grants her leniency, in which case she would get life in prison and may not be eligible for parole for at least 25 years.

If the prosecution can't prove premeditation, as is required for a first-degree murder charge, Arias could still be convicted of second-degree murder, commanding 10 to 22 years in prison. The jury can also decide that Arias killed Alexander recklessly or that he attacked her. She'd then be convicted of manslaughter.

Lastly, the jury could find her not guilty or determine that she acted in self-defense and that her actions were reasonable.

Followers of the trial have driven for hours to watch the courtroom drama in person. Spectators began lining up at 1 a.m. Friday -- more than six hours before the courthouse opened -- to get a seat, according to CNN affiliate KPHO.

Until April 25, the public was given access on a first-come, first-served basis, but the judge changed it to a lottery system for closing arguments, the station reported.

CNN's Ted Rowlands, Ashleigh Banfield and Eliott C. McLaughlin and HLN's Graham Winch contributed to this report.

™ & © 2013 Cable News Network, Inc., a Time Warner Company. All rights reserved.