SALINAS (CBS)- “What happened to Kristin Smart?” The answer, according to prosecutors, will be outlined during the course of the trials for the two men charged in connection to her disappearance, the first glimpse of what’s to come detailed in opening statements on Monday.

Prosecutors told the jury that Paul Flores, a Cal Poly student in 1996, now 45, murdered Smart, 19, while he attempted to rape her in his dorm room over Memorial Day weekend 1996.

“The evidence will show that Kristin was murdered by Paul Flores,” said Deputy District Attorney Christopher Peuvrelle. He told the jury Ruben Flores would tear down missing posters of Kristin and speak derogatively of her, “all while her corpse was decomposing underneath his deck.”

On May 24, 1996, Smart wanted to be find a party or event and be social, according to testimony prosecutors say the jury will hear more about in the coming weeks. Smart recruited Margarita Campos, who lived in Smart’s dorm, Muir Hall, to join her in finding a social event on a Friday night.

Smart would later be last seen alive leaving an off-campus party headed back towards her dorm alongside three other students. When two of the students broke away, Smart was left alone with Flores.

Peuvrelle said Campos, to this day, “regrets leaving her friend [Smart] to go off to this party by herself.” She would later tell prosecutors she noticed that Paul Flores was “unnaturally interested in Kristin.”

Another friend of Smart’s, Steve Fleming, who was a basketball player at Cal Poly, told prosecutors he noticed Paul would walk through the halls at Muir Hall, where Smart lived. This was strange to Fleming, Peuvrelle told the jury Monday, because Paul lived in Santa Lucia Hall, another on-campus dorm.

When Smart left the part on that Friday in 1996, Peuvrelle described Smart as “incapacitated” and “barely able to move” without help. This incapacitation, he told the jury, came from what she drank at the off-campus party. Peuvrelle laid out a timeline of what evidence will show jurors in the course of the trial.

Flores, prosecutors say, was “not invited” to the off-campus party and had a short interaction with Smart at the party. Prosecutors said Smart was “too nice” to Flores, the man they say is her killer.

The prosecutors outlined a timeline of Smart’s night that Friday, after she left Campos and arrived to an off-campus house between 10-10:30 p.m. She was found face down, incapacitated between 12-12:30 a.m. in the front yard of the home, when friends say they helped her up to walk her back to her dorm, closer to 2 a.m. The two friends, joined by Paul Flores, and Smart, headed toward the dorms.

Attorney for Paul Flores, Robert Sanger, told the jury in opening statements that the last time Flores saw Smart, she was alive and capable of walking on her own back to Muir Hall. Witnesses told prosecutors Flores said he would get her home safely. The prosecutors said Monday a witness would later recall that Flores, “never asked Tim Davis where Kristin lived,” when he offered to walk her home.

Instead, prosecutors said Flores took Smart towards his dorm and she was not seen alive again, “Kristin never came home.”

As the weekend went on, Smart’s family didn’t hear from her on their “ritual” Sunday call and her friends grew increasingly worried. “They all looked forward to that phone call,” Peuvrelle said.

TODAY: Opening Statements in the trial for Paul and Ruben Flores will begin at the Monterey County Courthouse.

They’re here because of the murder of #KristinSmart, 26 years after she disappeared as a freshman at Cal Poly. @CBSSacramento pic.twitter.com/xci8f33McT

The phone call that was made, Peuvrelle said, was from Paul Flores to his father, Ruben Flores, to help him hide the truth.

Paul Flores has a history of “predatory behavior” towards women, Peuvrelle said, that included three women who say they were drugged at bars in Southern California and then sexually assaulted by Flores, all within the last decade.

Smart’s body has still never been found and investigators believe her body was originally put in a grave in Ruben Flores’ backyard, but later moved before authorities searched the home in 2020. In 2021, the father and son were arrested in connection to Smart’s disappearance, Paul for murder and Ruben for accessory to the crime, both pleaded not guilty.

Deputy District Attorney Christopher Peuvrelle with the San Luis Obispo County District Attorney’s Office gave both opening statements to each jury. The father and son’s cases are being tried separately, each with their own jury, but the cases are being heard together.

He used the Sunday marker to measure the amount of time the Smart family has been without their eldest daughter, Kristin, and the impact its had on their family. He set the scene for testimony from her parents, Denise and Stan, and siblings, Lindsey and Mark, that is expected to take place this week.

Paul Flores is represented by Robert Sanger, who responded to many of the prosecution’s statements about Flores and his history, especially his relationship with women. Sanger said it is “believed by now” that Smart is deceased and there is “no evidence what happened to her after Paul Flores left her at the dorms.”

Sanger points the jury to the evidence, or as he explained, the lack thereof: “There is no body, no physical evidence, no forensic evidence,” he said.

Sanger said, while it was difficult to speak of someone who is not able to speak for themselves, Smart had a history of “going off with men, older men.” Sanger said Smart’s parents were “at their wit’s end with it” at the time she disappeared.

Peuvrelle told Ruben’s jury that investigators found a “treasure trove” of Kristin Smart memorabilia, like article clippings, missing posters, and letters the Smart family sent to the Flores’s, in Ruben’s bedroom during a 2020 search of his home.

In response, during his own opening statement, Sanger said there was a “concerted” media campaign, “they didn’t have any evidence, but they decided, this was the case.”

Sanger said there was pressure on the Flores family for two decades in connection with the case, as many “gawkers” and “protesters” would appear at their home.