A preliminary hearing in the Kristin Smart murder case began Monday with an emotional testimony from her mother as she fielded questions from California prosecutors about her relationship with the missing college student. 

Denise Smart spoke about her other children and how Kristin missed out on major milestones and accomplishments and the efforts by her and her husband to find their daughter, a 19-year-old California Polytechnic State University student who vanished on May 24, 1996 while walking home from a party.  

"She always felt like a gift to our family," Denise Smart said. "She was so energetic and had a great smile. She was the best hugger."

The hearing is part of the criminal case against Paul and Ruben Flores, who both appeared in court, and is expected to last 12 days, the San Luis Obispo Tribune reported. 

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Kristin Smart, middle, Paule Flores, left and Ruben Flores, right. (San Luis Obispo County Sheriff’s Office)

Paul Flores, 44, was the last person seen with Smart. They were both freshmen at the college when she disappeared. Prosecutors allege he killed her during an attempted rape in his dorm room. 

Ruben Flores, Paul's 80-year-old father, is charged as an accessory and is alleged to have helped conceal the body. 

Both have pleaded not guilty. More than two dozen women have accused Paul Flores of sexual misconduct over the years, according to court documents. 

Smart's body has never been recovered but prosecutors believe it was buried on the property of Ruben Flores and recently moved. 

Paul Flores, left, appears at his arraignment, with attorneys Robert Sanger, center, and Sara Sanger, right, both representing him in the preliminary hearing Monday, in San Luis Obispo, Calif. Flores is charged in the killing of Kristin Smart, a Cal Poly student who disappeared in 1996.  (David Middlecamp/The Tribune San Luis Obispo via AP, Pool)

Under cross-examination by defense attorney Robert Sanger, attorney for Paul Flores, Denise Smart said her daughter had visited Thailand once on a family trip and never said anything about wanting to visit the country in the spring of 1996. An attorney for Ruben Flores asked Smart's mother if she was aware of three alleged sightings of her daughter at Taco Bell restaurants. 

She said she was not. She was also asked if she was aware Kristin Smart went missing briefly while working as a lifeguard in Hawaii, according to the Tribune. 

Denise Smart testified that her daughter didn't have the financial means or resources to leave and disappear. 

She said Kristin wasn't "particularly happy" at the university earlier in the year but was more optimistic when the family saw her that spring. She said the school was not aware Smart was missing when the family contacted them.

At the conclusion of the hearing, Superior Court Judge Craig van Rooyen will rule whether prosecutors have established probable cause to proceed to trial. 

Ruben Flores, father of Paul Flores, sits in court on Monday in San Luis Obispo, Calif. Paul Flores is charged in the killing of missing Cal Poly student Kristin Smart.  (San Luis Obispo via AP, Pool)

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Other witnesses expected to testify during the hearing include investigators, witnesses, cadaver dog experts and women who have accused Paul Flores of sexual assault. 

Paul Flores faces up to life in prison if convicted of first-degree murder. His father faces up to three years for the accessory charge. He remains out on bond.