PHOENIX - The judge in the Jodi Arias murder trial declared a mistrial in the penalty phase Thursday after the jury reported for a second time that it was deadlocked on whether to sentence her to life in prison or death for killing her boyfriend in 2008.

The judge scheduled a retrial for July 18. A new panel likely will be seated to try again to reach a decision on a sentence - unless the prosecutor agrees to a life sentence.

The jurors began deliberating Tuesday and first reported they had failed agree the next day. The judge instructed them to keep trying.

The same panel on May 8 found Arias guilty of first-degree murder in the death of Travis Alexander, who was stabbed and slashed nearly 30 times at his Mesa home. The jury later determined the killing was cruel enough to merit consideration of the death penalty.

Under Arizona law, a hung jury in the death penalty phase of a trial requires a new jury to be seated to decide the punishment. If the second jury cannot reach a unanimous decision, the judge would then sentence Arias to spend her entire life in prison or be eligible for release after 25 years. The judge cannot sentence Arias to death.

Former Maricopa County Attorney Rick Romley has said the case could drag on for several more months as the new jury reviews evidence and hears opening statements, closing arguments and witness testimony in a "Cliffs Notes" version of the trial.