Paul Flores, Kristin Smart and Ruben Flores.Photo: San Luis Obispo County Sheriff’s Office/AP/Shutterstock; Facebook

Paul Flores, Kristin Smart, Ruben Flores

Friends ofKristin Smarttestified Monday thatPaul Floresseemed to have an unusual interest in his classmate well before the California Polytechnic State University freshman disappeared in 1996 after leaving an off-campus party.

Paul Flores, 45, the last person allegedly seen with Smart, would often “follow” the 19-year-old freshman, her friend Steven Fleming testified Monday in Monterey County Superior Court,The Tribuneof San Luis Obisporeports.

Prosecutors have said Flores raped and killed Smart on May 25, 1996, as she made her way back to her dorm, Muir Hall, authorities say.

He allegedly volunteered to walk her back to her room but she was never seen again.

Kristin Smart.Axel Koester/Sygma via Getty

Kristin Smart went missing on May 25, 1996 while attending California Polytechnic State University, San Luis Obispo and has not been heard from since

Though her body was never found, she is presumed dead. After a lengthy investigation, Paul and his father, Ruben Flores, 81, were arrested in April 2021. Paul is charged with first-degree murder.

Ruben is charged with accessory after the fact to the crime of murder and accused of burying Smart’s body in his yard before moving it, prosecutors have said.

Paul’s attorney has said the prosecution has a weak case. Ruben’s attorney told PEOPLE his client is innocent.

Paul Flores.Daniel Dreifuss/Monterey County Weekly via AP

Paul Flores listens during his murder trial in Monterey County Superior Court in Salinas, Calif., Monday, July 18, 2022. Flores is accused of the murder of Kristin Smart and opening statements were expected Monday. Smart is still missing, but the man last seen with her at California Polytechnic State University in San Luis Obispo in 1996 is on trial more than a year after he was arrested on a murder charge along with his father, who is accused of helping hide her body.

On Monday in court, Smart’s roommate, Crystal Teschendorf, who was known as Chrystal Calvin in college, testified that she became worried the night Smart vanished when she failed to return to their dorm room.

She said she became concerned when she saw Smart’s backpack and keys still in the dorm room in the same place they’d been the night before,KEYTreports.

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“For her to not come back without anyone knowing was unusual,” Teschendorf testified, KEYT reports.

Kristin Smart’s family.Axel Koester/Sygma via Getty

Kristin Smart went missing on May 25, 1996 while attending California Polytechnic State University, San Luis Obispo and has not been heard from since

With Smart still missing on Tuesday, May 28, Teschendorf called police again, saying she believed that for Smart to go missing was “out of character.”

Smart was in “a good mood” when she left at about 8 p.m. for the parties she planned to attend on the night of May 24, 1996, Teschendorf testified.

She never saw Smart alive again.

Kristin Smart.Facebook

Kristin Smart

The Flores' trial began on July 18 and is expected to last about four months.

The trial was supposed to take place in San Luis Obispo County, where the alleged crime took place, but a judge ruled in favor of a request to move to another county to guarantee that Paul and Ruben would receive a fair trial,The Tribunereports.

source: people.com