A California man known as the “NorCal Rapist” who committed a series of brutal attacks over a 15-year-period will now live the remainder of his life behind bars after receiving a 897-year sentence on Friday. 

Roy Charles Waller, 60, was convicted last month on 46 counts related to kidnap, forcible rape, oral copulation, sodomy and foreign penetration, according to a Friday press release from the Sacramento County District Attorney’s Office. 

The charges involved assaults on nine women in six California counties, resulting in seven different cases between 1991 and 2006. 

The district attorney’s office added in Friday’s statement that the 897-year sentence is the maximum allowed by state law. 

CNN reported that Sacramento police detective Avis Beery said that in several instances, Waller would break into his victims’ homes, tie them up and repeatedly sexually assault them. Waller usually committed his attacks at night and occasionally would take the women to ATMs so he could rob them. 

In 2006, DNA evidence allowed police to link together six different cases, although law enforcement was not able to tie them back to Waller, as he was not in the state’s criminal offender database at the time, the district attorney’s office said Friday. 

However, in September 2018, biological evidence left at one of the crime scenes was used along with investigative genetic genealogy (IGG) to create a specialized DNA profile. 

Investigators were then able to use this profile to track down potential relatives of the perpetrator and, by constructing family trees, zeroed in on Waller. 

This technology was also used to track down the Golden State Killer, who was sentenced to life in prison in August. 

Following Waller’s conviction last month, Joe Farina, the man’s defense attorney, said the DNA evidence placed a significant challenge for Waller’s defense. 

"It didn't matter what I did," Farina said, according to CNN. "It was a DNA case. We could not overcome the fact that his DNA was at nearly all the crime scenes."

Farina told CBS affiliate KPIX on Friday that Waller maintained his innocence and said he would be appealing the sentence. 

The district attorney’s office on Friday said that all nine of Waller’s victims testified during a month-long jury trial, as well as retired officers, detectives and sexual assault forensic nurse examiners from multiple states. Friday’s news release noted that some of these witnesses were long retired and are currently in their 80s. 

“The victims waited for decades for justice and it was only through the use of IGG that the identification and arrest of Waller was possible,” the attorney’s office said in the press release, adding that it “would like to thank the original detectives from agencies in each jurisdiction on these cases who never gave up pursuing the offender.”