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Boyfriend of missing Phoenix woman sentenced to 25 years for her murder

Robert John Interval, the boyfriend of the presumed-dead Christine Mustafa, was sentenced Friday to 25 years in prison for her murder.

PHOENIX — Robert John Interval, the boyfriend of the presumed-dead Christine Mustafa, was sentenced Friday to 25 years in prison for her murder. 

Judge Stephen Hopkins delivered the sentence after a monthslong trial that resulted in Interval's second-degree murder conviction. 

A jury found Interval, 37, guilty back in April. He was tried on one count of first-degree murder, but the jury could not come to a conclusion on that charge. He was found guilty of second-degree murder. 

RELATED: Jury finds Robert Interval guilty in death of girlfriend Christine Mustafa

Mustafa has been missing since May 10, 2017. 

Family and co-workers alerted police about her disappearance after Mustafa did not show up to work the next day. Interval told police that Mustafa had left for work, but could not explain why her car was still at the house. 

Investigators combed through 1,600 tons of debris in the State Route 85 landfill in Phoenix -- where police believe Interval dumped her body -- months after she was reported missing, but the search came up empty. 

PREVIOUSLY: Phoenix PD finds no leads on missing woman in landfill search

Her body has never been found. She was 34 when she went missing. Mustafa and Interval also had a child together. 

During the trial, which began in February, prosecutors described Interval as a paranoid boyfriend who believed Mustafa was cheating on him. 

Concerned family and co-workers told investigators that the couple had not been getting along and that Mustafa was looking to safely distance herself from Interval. 

Officials said Mustafa contacted Phoenix police the day before she vanished and asked how to get a restraining order against Interval.

Prosecutors also said Interval bought mattress covers the day Mustafa disappeared and was seen outside a trash transfer facility later that day. 

RELATED: Murder trial begins for the man police say killed Christine Mustafa

12 News' Alejandra Armstrong contributed to this report.