Nick McGuffin, who was Leah's boyfriend at the time of her death in 2000, is expected to stand trial for her murder on May 10, 2011.
ABC News' "20/20" was given exclusive access during the re-opening of this decade-old cold case with a fresh investigative team, including on the day police went in to apprehend McGuffin, the person they had suspected from the beginning.
After a grand jury's indictment was handed down, police arrested McGuffin on Aug. 24, 2010 and charged him with murder.
When police arrived at McGuffin's home, he was retrieving his mail and still wearing a uniform from his job as a short-order cook. He stood quietly as police read him his rights and handcuffed him.
"I didn't do it. Love of my life, man," he told "20/20" at the time of his arrest. "They have nothing else to go on, and I'm the boyfriend."
McGuffin pleaded not guilty and continues to maintain his innocence. His bail was set at $2 million.
Leah was a high school freshman when she disappeared in August 2000 after leaving a friend's house. Police initially treated the disappearance as a runaway teen case. Weeks later, the girl's decomposing body was found on a wooded roadside slope a few miles outside town.
Authorities said circumstantial evidence initially pointed to then-18-year-old McGuffin. But there was no hard evidence to link him to the crime.
Leah's best friend, Cherie Mitchell, said she thought Leah's relationship with the high school senior was bad for her.
"I think that he was kind of dangerous and, you know, maybe she liked the danger side of him," Mitchell said.
Leah's mother, Cory Courtwright, said that she did not approve of her daughter's relationship either.
"I found out that they were being sexually active, and that was disturbing for me," Courtwright said.
On the night of Leah's disappearance, Mitchell confronted her friend and told Leah she should break-up with McGuffin. Furious, Leah stormed out. She last was seen walking alone near a gas station in downtown Coquille, but she never made it home.
Former Police Chief Mike Reeves, who was head of the town's police department in 2000, turned down several requests to be interviewed, but recently told ABC News' Jim Avila that five days passed after Leah was reported missing before he was convinced of foul play.
Two blood-splattered gym shoes found miles apart had surfaced during that time and it would take investigators another month to find her body, but still no arrests were made.
As the years dragged on, the small community of Coquille, a town of about 4,000 residents, became more furious that Leah's murderer hadn't been caught.
A new police chief, Mark Dannels, vowed to solve the case and a team of forensic experts known as the Vidocq Society, based in Philadelphia, was brought in to advise on the case.
A crime-solving team made up of former FBI special agents, police officers, forensics experts and profilers, the Vidocq Society specializes in solving cold cases. One of the members, forensic pathologist Richard Walters, traveled to Oregon to review the evidence early last spring.
After reexamining Leah's bloody shoes and how her body was dumped, Walters labeled Leah's killer a "power assertive crime type."