SACRAMENTO — Prosecutors in the college town of Davis are combing through three case files from the summer of 1978 — a time when fear gripped the region as a rapist struck time and again — to determine whether they can add sex-assault charges to the crimes attributed to the Golden State Killer.

Authorities said they are assessing whether they can add the rape charges despite a three-year statute of limitations that was in effect during the late 1970s, when the Davis sex assaults and many others attributed to the man also known as the East Area Rapist were committed. Prosecutors in Davis and other jurisdictions say they may be able to get around the charging deadline in the case of Joseph James DeAngelo, who has already been charged with two murders and faces possible accusations in up to a dozen killings.

One question they must wrestle with is whether doing so could delay the day of justice for the survivors of the people DeAngelo is suspected of killing up and down the state in the 1970s and ’80s.

“Prosecutors have to make the difficult decision of what cases to pursue,” said Robert Weisberg, a professor at Stanford Law School and an expert on criminal law. “Vindicating (rape) victims can slow the judgment.”

DeAngelo, 72, was arraigned Friday on two murder charges in Sacramento County. He has not entered a plea and is expected to return to court Thursday, when his public defender will try to stop law enforcement from collecting more DNA from DeAngelo and from taking photographs of his body. Prosecutors in Ventura, Orange and Santa Barbara counties are expected to file additional murder charges for crimes committed there.

It’s unclear how many — if any — of the 45 rapes attributed to the Golden State Killer will be included in the case. Most of the rapes in the ’70s occurred in Sacramento County, a few miles from where DeAngelo was arrested at his home last week in Citrus Heights.

“They can’t try every case or the case would go on for years,” said Ken LaMance, a San Francisco attorney who has written about California’s complex laws on statutes of limitations. “One murder conviction is enough to keep him in jail for the rest of his life.”

Jonathan Raven, chief deputy district attorney in Yolo County, said authorities there have not ruled out filing charges in the Davis rapes.

“Our main focus is to solve this crime, and bring some sense of justice to the victims,” Raven said.

All of the Davis rapes took place within a little more than a month in 1978. The first attack happened June 7, when a 21-year-old UC Davis student was raped in her apartment north of campus around 4:30 a.m. On June 24, a 32-year-old woman was attacked, followed by the rape of a 33-year-old woman two weeks later.

Investigators have remained in contact with the victims, Raven said. DeAngelo’s arrest “has opened up a whole host of emotions for them in a positive sense that the rapist was likely found, but also reopening the wounds and retraumatizing them,” the prosecutor said.

There has never been a statute of limitations for murder in California. But until 1981, prosecutors seeking rape convictions had to bring a case within three years of the crime. That year, Santa Clara County prosecutors said they were unable to bring charges in several sexual assaults they attributed to Melvin Carter, who confessed to more than 100 attacks in the College Terrace neighborhood of Palo Alto and other cities in the 1970s but served just 12 years in prison.

The Legislature responded by doubling the statute of limitations for rape to six years. In 2000, lawmakers increased the time limit again, this time to 10 years, before doing away with it entirely in 2016. The law now allows a rape committed after Jan. 1, 2017, to be prosecuted at any time.

“The old statute of limitations laws were complicated and convoluted,” said state Sen. Connie Leyva, D-Chino (San Bernardino County), who authored the bill that ended the statute of limitations on sex crimes.

“It’s much more straightforward now,” she said. “It’s cases like (the Golden State Killer) that show why we needed to do this.”

However, Leyva said, the law can’t be applied retroactively.

Prosecutors in the case against DeAngelo will be limited to the laws on the books when each crime was committed. For most of the rapes, that means the statute of limitations was three years. But criminal law experts and Raven, the Yolo County prosecutor, said there is an exception to that cap.

There is no statute of limitations for crimes with life sentences. That could mean rapes in which the attacker used a knife or gun could fall outside of the statute of limitations, they said.

Many victims of the serial rapist reported that he held a knife to their throat and threatened to kill them.

Raven said he could not comment on whether a weapon was used in the Davis rapes, but said the circumstances were consistent with what victims reported in other cases linked to the serial rapist.

Among the many women believed to have been victimized by the rapist is Margaret Wardlow, who was 13 years old when she was raped in her bedroom just outside Sacramento in 1977, when the statute of limitations was three years.

She said she’s at peace with the possibility her attacker may never be prosecuted for what he did to her. It’s enough knowing that after 40 years there is a suspect linked to so many heinous crimes, she said.

“We will see where the evidence is strongest, and that is where they will prosecute him,” Wardlow said.

“Do I care if my case is prosecuted? No. But I will be at the trial.”

Melody Gutierrez is a San Francisco Chronicle staff writer. Email: mgutierrez@sfchronicle.com Twitter: @MelodyGutierrez