The judge declared a mistrial and will sentence Arias to either life in prison or a life term with the possibility of release after 25 years.
It marked the second time a jury has deadlocked on her punishment — a disappointment for prosecutors who argued for the death penalty during the nearly seven-year legal battle against Arias.
Arias was convicted of murder in 2013 after a lengthy trial that became a sensation with its tawdry revelations about her relationship with victim Travis Alexander.
The victim’s sister, Samantha Alexander, sobbed in court while the decision was announced.
The jurors deliberated for 26.5 hours over a five-day span. Earlier this week, Arias’ attorneys said jurors were at an impasse, but the judge denied a mistrial request. A verdict does not rule out the possibility of a hung jury.