Helping fuel the gay hate crime theory were statements made to police and the media by Kristen Price, McKinney's girlfriend. (Price was charged with felony accessory after-the-fact to first-degree murder. She later pleaded guilty to a reduced charge of misdemeanor interference with police officers.)
Price now says that at the time of the crime she thought things would go easier for McKinney if his violence were seen as a panic reaction to an unwanted gay sexual advance.
But today, Price tells Vargas the initial statements she made were not true and tells Vargas that McKinney's motive was money and drugs. "I don't think it was a hate crime at all. I never did," she said.
Former Laramie Police Detective Ben Fritzen, one of the lead investigators in the case, also believed robbery was the primary motive. "Matthew Shepard's sexual preference or sexual orientation certainly wasn't the motive in the homicide," he said.
"If it wasn't Shepard, they would have found another easy target. What it came down to really is drugs and money and two punks that were out looking for it," Fritzen said.
Asked directly whether he targeted and attacked Shepard because he was gay, McKinney told Vargas, "No. I did not. ... I would say it wasn't a hate crime. All I wanted to do was beat him up and rob him."
But if the attackers were just trying to rob someone to get a drug fix, why did they beat Shepard so savagely?
Rerucha attributes McKinney's rage and his savage beating of Shepard to his drug abuse. "The methamphetamine just fueled to this point where there was no control. It was a horrible, horrible, horrible murder. It was a murder that was once again driven by drugs," Rerucha said.
Dr. Rick Rawson, a professor at UCLA who has studied the link between methamphetamine and violence, tells "20/20" the drug can trigger episodes of violent behavior.
"In the first weeks after you've stopped using it, the kinds of triggers that can set off an episode are completely unpredictable. It can be: you say a word with the wrong inflection, you touch someone on the shoulder. It's completely unpredictable as to what will set somebody off" Rawson said.
"If Aaron McKinney had not become involved with methamphetamine, Matthew Shepard would be alive today," Rerucha said.
Another widely held belief about the case is that McKinney and Shepard had never met before their fateful encounter at the Fireside Lounge. But a number of sources tell "20/20" the two were not strangers.
"Everybody knew Matt Shepard was a partier just like Aaron, just like the rest of us," said Bopp.
In fact, Bopp said he had seen Shepard and McKinney together at parties. "Aaron was selling [drugs] and him and Matt would go off to the side and they'd come back. And Matt would be doing some meth then," he said.
Though they frequented the same party scene, McKinney maintains he had never met Shepard before the night of the crime and wonders why people might say he had. "I've never met him. ... Maybe they seen us somewhere in the same spot or something. I don't know," McKinney said.
A bartender familiar with the local drug scene, who asked to be identified only as "Jean," says she was friendly with Shepard. She also says McKinney and Shepard knew each other.