Wynetta Davis' death 25 years ago at the hands of unknown assailants might have forever gone without answers. The 26-year-old woman's body was found in a livestock water trough northwest of Petaluma. No suspects were identified.

More than two decades later, DNA evidence found by detectives who delved back into the 1988 case files led investigators to arrest two men who are now prime suspects in the slaying.

The case will now unfold in Sonoma County Superior Court, possibly bringing closure to the Davis family if the men are found guilty in the killing.

"I want to know why ... why," said Davis' eldest sister, Marilyn Davis Jones, 57, of Vallejo. "I can't imagine her doing anything to them in the first place to make them want to kill her."

Her other sister, Carlene Davis Taylor, 56, of Houston said that not having answers pained her family over the years. She wanted to call "Most Wanted" TV shows to raise awareness about her sister's case, but without suspects there was nothing she could do.

"I'm so grateful," the case is moving forward, Taylor said. "We were best friends."

The Sonoma County Sheriff's Office announced Wednesday that Josafat Presencion, 47, and Fausto Chavez, 49, were in custody at the Sonoma County Jail on suspicion of Davis' murder.

Presencion and Chavez pleaded not guilty Aug. 16.

The men, both Mexican nationals, were living in Vallejo in 1988, as was Davis, Sgt. Carlos Basurto said.

Davis lived on Grant Street in south Vallejo with her mother, Mary Davis, and two sons, aged about 2 and 5, her sisters said. Her sisters lived across the street.

On May 11, 1988, Davis left the house as night fell to buy diapers at a bodega around the corner, according to her family. Taylor said she ran out of the house to join Davis a few minutes later, but her sister was gone.

"I ran over to the store and said, 'Did you see my sister?' Taylor said. "He said, 'She didn't come in here.'"

Taylor said the next day she walked around the neighborhood with a photograph of Davis but found no answers to her sisters' whereabouts.

Davis was reported missing May 16, Basurto said.

Nearly 40 miles away in Sonoma County, detectives were investigating a woman's body found May 13, 1988, in a livestock water trough at a Pepper Road property just north of Bodega Avenue, Basurto said

State technicians identified the body as Davis' through fingerprints May 19, three days after she was reported missing, according to the Sheriff's Office.

The cause of death was asphyxiation, and it appeared she had been strangled, Basurto said.

But no suspects were identified.

"The case was a true whodunit," Basurto said.

In May 2010, sheriff's detectives began looking through the department's unsolved investigations "to see what there was, if anything, that could be re-analyzed or analyzed for the first time," given advances in DNA science, Basurto said. "Things they couldn't have done in 1988."

They sent evidence from Davis' case to a state Department of Justice DNA lab for additional testing. Basurto declined to describe what kind of evidence contained DNA from the suspects.

The next year, "we got a hit," he said.

Presencion and Chavez were identified through the searchable DNA database CODIS, or Combined DNA Index System used by law enforcement across the country, in February and March of 2011.

At that time, both men were incarcerated for other crimes. Presencion was at San Quentin State Prison, according to state records, and Chavez was housed at an Alabama facility.

Details about their convictions weren't immediately available. Presencion has been in state prison since June 19, 1989, according to California Department of Corrections and Rehabilitation records.

With two suspect names, sheriff's detectives launched into a re-investigation of the 1988 case, which involved finding people who knew the suspects and victim at that time, Basurto said.

Murder complaints and fugitive warrants were issued for the men July 1 in Sonoma County Superior Court. Chavez was booked into the Sonoma County Jail on July 13 and Presencion arrived Aug. 13, jail officials said. Jail records listed Chavez's last name as Chavez-Pandruo.

The men are next in court Nov. 1 for a hearing to determine whether they must provide additional DNA samples, said Santa Rosa attorney Geoffrey Dunham, who is representing Presencion.

Prosecutors "are going to have to present probable cause," beyond the DNA evidence, Dunham said.

Basurto said the Sheriff's Office didn't announce the arrests in the case, even after the men were in local custody and charged with murder, until they had tracked down family members of the victim and finished certain aspects of the investigation.

You can reach Staff Writer Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.