DNA leads to arrest in graduate student's 2004 murder after yearslong investigation

University of Tennessee graduate student Johnia Berry was brutally stabbed to death in her Knoxville apartment in 2004, in a case that remained unsolved for years.

The 21-year-old was fatally injured in her apartment around 4 a.m. on Dec. 6, 2004, after an intruder entered and stabbed her repeatedly.

The attack woke her roommate, Jason Aymami, who was also stabbed when he emerged from his bedroom. Despite his injuries, he managed to escape to a nearby convenience store and call 911.

Berry, who was found clinging to life in the entryway of her apartment complex, died in the ambulance before reaching the hospital.

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The first thing that stood out to police at the scene was the amount of blood at the crime scene -- officers found blood spatter on the doorknob, the floor and the bedroom door.

"Could it have been a friend of theirs that was in the apartment?" Knox County Sheriff's Office Captain Brad Hall told "20/20." "Was it somebody that had gotten upset with Jason or Johnia? There's a lot of different theories that were being thought about, of what could have happened."

Investigators discovered the knife used in the stabbing in the hallway outside Berry's bedroom.

"What stood out to me the most about the weapon is how damaged it was," Knox County Sheriff's Office Detective AmyLynn Delgado told "20/20." "It was a small steak knife, but the handle was broken. The blade was bent. I could only assume that it had hit bone, that it was used multiple times, that it was very violent, just given the force to break the handle."

The autopsy revealed Berry had been stabbed approximately 26 times, with wounds to her neck, head, face, chest, back and legs.

Due to the number of times Berry had been stabbed, detectives believed the attack was personal. They thought the assailant was likely someone who knew her and wanted her dead.

"We really focused mostly on her closest circle," Delgado said.

Berry's fiancé was cleared after investigators found cell phone records confirmed he was in Michigan at the time of the murder.

Investigators then turned their attention to her roommate, Aymami. When questioned about his relationship with Berry, Aymami said there was no romantic interest.

Aymami told investigators he had been watching TV when Berry went to bed that night. During his interview, he provided crucial information: he had seen the killer face-to-face.

Based on Aymami's description, investigators created a composite sketch of the suspect, which generated significant public interest. Detectives ultimately cleared Aymami.

"We called every day," Berry's mother Joan Berry told "20/20." "We would call the detectives. There was that feeling that detectives and the sheriff's office weren't doing enough, when in reality they were working this every day. There just weren't any answers."

The case remained unsolved for several years, despite numerous tips and offered rewards.

The breakthrough came in April 2007, when someone who recognized the composite sketch on a billboard contacted police. That tip led police to Taylor Lee Olson, a man in his early 20s with a history of petty crimes.

While Olson initially denied involvement, investigators determined that his DNA matched evidence taken from various locations inside and outside the apartment.

Olson ultimately confessed under questioning. He admitted to entering Berry's apartment through an unlocked back door, saying he was looking for car keys during an attempted theft, according to officials.

He was charged with felony murder, first-degree murder, attempted first-degree murder and aggravated burglary.

Before the case could go to trial however, it took a final dark twist.

"I got a call the Monday after Easter that he had been found in his jail cell," Kevin Allen, a Knox County assistant district attorney general, told "20/20." "That he had fashioned a ligature with sheets and had hung himself."

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