Breakthrough DNA evidence finally unravels cold case of student found brutally stabbed in apartment

The case of a brutal murder of a University of Tennessee graduate student had gone cold, and after the lead investigator died in a car crash it seemed as if it was never going to be cracked.

But authorities were granted a breakthrough on the case some years later thanks to DNA evidence, due to the blood-soaked crime scene.

In the early hours of December 6 2004, 21-year-old Johnia Berry was stabbed more than 20 times to the face, head, neck, back, chest and legs - so hard in fact that the murder weapon, a steak knife, was left bent and broken.

The incident took place at around 4am, and her roommate Jason Aymami managed to escape with his life after the brutal attack woke him and he emerged from his bedroom.

After he was also stabbed by the attacked, Aymami fled his home and dialled 911 from a convenience store nearby.

When the emergency services reached Berry's home in the Tri-Cities area, she was found in the entryway to her apartment close to death.

Tragically, Berry died on the way to hospital - shortly before she was due to graduate with a master's degree from East Tennessee State university.

The case has recently been put back under the spotlight, through ABC's 20/20 special that aired on Friday (May 16), titled 'Blood on the Door'.

Knox County Sheriff's Detective AmyLynn Delgado told the TV crew: "What stood out to me the most about the weapon is how damaged it was.

"It was a small steak knife, but the handle was broken. The blade was bent... it was very violent, just given the force to break the handle."

Johnia Berry was 21 years old when she was brutally murdered (Family handout)

Due to the sheer aggression behind the killing, investigators were adamant that Berry must have known her killer, and so their attention turned to her fiancé.

"We really focused mostly on her closest circle," Delgado explained. However, her partner had a clear alibi and his phone records backed it up - he was 700 miles away in Michigan at the time of the murder.

The only thing they had on Berry's twisted killer was that Aymami had seen him in person, describing him as being 5'8" tall and weighing 150 pounds.

A sketch was made by a forensic artist and it was subsequently part of a billboard campaign to help track him down in May 2005, with a reward for any information leading to an arrest - which was upped to $60,000 by the end of the year.

After conducting more than 300 interviews and taking around 80 DNA samples, cops were no closer to cracking the case - and they still did not even have a motive.

Photos inside Berry's parent's home depict her as a child and with her fiancé (ABC)

Then tragedy struck again, this time in the form of the lead investigator, assistant chief Keith Lyon, dying in a car crash while on duty in May 2006.

Berry's mom Joan told 20/20: "We called every day.

"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."

It wasn't until April 2007, almost three years on from Berry's death, that detectives had a breakthrough in the case - thanks to the billboard campaign.

Police had a tip off that Taylor Lee Olson matched the sketch, who was 21 years old at the time. He had a history of committing minor crimes.

Taylor Lee Olson was charged with the murder of Berry, but took his own life before his trial began (WJHL)

The only problem was that he was much taller than Amyami's description - he was a scaling 6'3", and his DNA hadn't been on record.

However, in July of that year Olson was arrested for something completely unrelated, and voluntarily submitted his DNA.

Detectives were finally able to place him at the scene of the crime thanks to his DNA, and on September 21 he was taken into custody at West Town Mall.

According to officials, at first Olson denied having any involvement in Berry's death before later breaking and admitted to having entered her apartment through the back door - which he found was unlocked.

He explained he was looking for the car keys during the theft that went wrong. He was indicted on seven charges, including attempted murder of Aymami, aggravated burglary and the first-degree murder of Berry.

Before his trial could commence, Olson died by way of suicide while in police custody, in March 2008.