Her mother could tell the 21-year-old was thrilled with her new legal assistant position. Here was a job that seemed to offer concrete proof that the sweet, bubbly young woman finally was getting her life back on track.

So when the firm called the next day to ask why Cave had not shown up for work, her mother immediately sensed something was wrong.

Her worst fears were confirmed when her daughter was discovered dead in a bathtub at an acquaintance's apartment. She had been shot in the chest, and her body was partially dismembered.

The acquaintance, Colton Pitonyak, a University of Texas student who had taken Cave to dinner on the night she was killed, goes on trial for her murder this week in Travis County Superior Court.

Prosecutors have a mountain of evidence against Pitonyak, including a surveillance tape showing his purchase of the hacksaw used to sever the victim's head and hands.

But the case still has its mysteries. Among them is motive.

Pitonyak, 24, and Cave had no history of discord. The crime scene, as gruesome as a horror movie, is difficult to reconcile with Pitonyak, a well-liked and intelligent finance major who had grappled with drug addiction, but had no record of violence.

Also unanswered is the role of Pitonyak's ex-girlfriend, Laura Hall, who ferried him to Mexico in her Cadillac after the killing. The 22-year-old woman, whom one friend said considered herself Bonnie to Pitonyak's Clyde, will face hindering apprehension charges at a later trial.

If convicted of murder, Pitonyak, a one-time National Merit Scholar, faces life in prison. He has pleaded not guilty to the charge.

Searching for Jennifer

The victim's mother, Sharon Cave, initiated a search for her daughter soon after receiving the call from the law firm on Aug. 17, 2005. She filed a missing persons report with the police and contacted her daughter's friends.

Jennifer Cave, whose family lived in Corpus Christi, first moved to the Austin area to attend Texas State University, but quit after one semester. She worked at a restaurant and took classes at a community college. Occasionally, she also used drugs.

Her roommate told Sharon Cave that Jennifer had not returned to their apartment from a date with a man named Colton. Increasingly worried, Sharon Cave obtained her daughter's cellphone records and dialed the numbers listed for the night of Aug. 16.

Among the people she called was Pitonyak, who told her that he had last seen her daughter when they had parted at midnight. He had no idea where she might be, he told her. But another friend contradicted Pitonyak.

Michael Rodriguez told Sharon Cave that he had talked briefly with her daughter an hour later — at 1:05 a.m. — and she was still with Pitonyak and he was behaving erratically. As they spoke, Rodriguez told police, it sounded as if the couple were walking through a parking lot and Cave was trying to calm Pitonyak, who, she said, had tried to break into one car and was urinating on another.

"Rodriguez stated Jennifer told him that Colton was very upset that he had lost his cell telephone and that she was going to help him find it. Rodriguez stated he asked Jennifer if she was okay, and she told him she was and that she would call him back," a detective who interviewed Rodriguez later wrote.

Cave never called her back, Rodriguez said.

Investigators went to Pitonyak's off-campus apartment and found both Cave's and Pitonyak's cars parked there. No one answered his door, however.

Police told Sharon Cave and her boyfriend, Jim Sedwick, that they lacked grounds to search his apartment and left the scene.

The next day, with Cave still missing and no sign of Pitonyak, Sedwick forced his way into the apartment.

"Sedwick advised officers he entered the apartment through the front window and began yelling for Jennifer. Sedwick advised as he walked through the hallway he smelled a foul odor and immediately realized something was wrong," according to a police report.

In the bathroom, Sedwick encountered a gory scene.

Jennifer Cave's bloody body lay in pieces in the bathtub. A hacksaw rested on her abdomen. Her chest was marked by knife wounds. An autopsy would later determine that she had been killed by a bullet that struck her right arm and torso. A second shot had been fired into her head after she was dead.

Toxicology tests showed Cave had methamphetamines, marijuana and alcohol in her system when she was killed.

Investigators summoned to the scene found a knife and a machete, both marked with blood, in the apartment. There was one bullet shell under her body and another on the coffee table in the living room.

Detectives traced the hacksaw to a hardware store, where they found a tape of Pitonyak strolling the aisles on Aug. 17, after Cave's death.

An employee told police that Pitonyak had smelled strongly of alcohol. The store owner said that when he had asked why Pitonyak needed the saw, he replied that he wanted to "cut up a turkey." He noted that Pitonyak also purchased ammonia, towels, carpet cleaner, large plastic bags, gloves, a face mask and odor eliminator.

Police filed a murder charge against Pitonyak and began searching for him. As they looked, authorities learned all they could about Pitonyak. He had grown up in Little Rock, Ark., and graduated from a Catholic high school there, where he had earned top grades and a scholarship to the University of Texas.

"He was a very bright student, and held a lot of promise," a former teacher told the Austin American-Statesman.

In recent years, however, Pitonyak seemed to jettison his clean-cut, academic image. On the popular social networking site Facebook.com, he used the screen name "ILoveMoneyAndHos" and listed his college graduation date as 2010 — nine years after he entered the university.

Among his favorite quotes was one from Al Capone: "You can get a lot farther with a kind word and a gun than a kind word alone."

Pitonyak also was in trouble for drugs. He did a stint in rehab, and in 2004, he was arrested for drug possession after police found cocaine and illegally obtained prescription sleeping pills and anti-anxiety medication in his apartment. He pleaded to a misdemeanor and served 20 days in jail, but his lawyer would later acknowledge he remained "up to his eyebrows" in drugs.

Using signals from his cellphone, police determined that Pitonyak had crossed into Mexico.

Another break came when the father of his former girlfriend and fellow University of Texas student, Laura Hall, contacted police. Loren Hall told investigators that four days after the killing, she had e-mailed him and asked to remove everything from her apartment. He suspected that she might be with Pitonyak.

Armed with this information, authorities combed border surveillance video and found an image of Hall's green Cadillac crossing into Mexico on Aug. 18 at 2:41 a.m., the night following Cave's murder.

On Aug. 23, Mexican authorities found Pitonyak and Hall in a Holiday Inn in the town of Piedras Negras. They drove the couple to the border, where Pitonyak was arrested by U.S. law enforcement agents and Hall was allowed to leave on her own.

Homicide detectives from Austin interviewed a hotel clerk who said the couple had asked him questions about Mexico's extradition policy and how they might sell the car to make some quick cash. The clerk, Pedro Fernandez, told the officers he was suspicious when the pair said they could not return to the United States to get the title for the vehicle.

"White people don't want to go back to their country? What's going on?" he said.

The same day as Pitonyak's arrest, a friend of Hall's phoned police and said that she was bragging about having helped Pitonyak. The friend, Said Aziz, told authorities that she said she was desperately love with him, to the point of seeing them as "Bonnie and Clyde," and believed that with her assistance, he might "walk" from the charges.

"She told him that she wanted to protect Colton and that she wanted to help him," according to a police report.

When Aziz expressed shock that she would try to assist "an axe-murderer," she replied that the death was "an accident" and said, "There is a big difference between manslaughter and first-degree murder."

Police quickly arrested Hall on charges of hindering apprehension.

Facing her own felony trial this year, Hall is not expected to be a witness for either side at Pitonyak's trial.

His lawyer had not specified a defense, but in comments during jury selection, he indicated that Pitonyak and Cave were "the best of friends." He said his client may take the stand to give his account of the events that lead to Cave's death.

The attorney, Roy Minton, also said he plans to ask the judge to allow jurors to consider two lesser charges: manslaughter and criminally negligent homicide.