Robert M. O'Ryan, 36, had been charged with felony stalking and commercial burglary of the 18-year-old Johnson, but had pleaded not guilty by reason of insanity. The Los Angeles Times said officials alleged he traveled from Florida to Los Angeles to find Johnson.
Officials said he scaled a fence at CBS Television City in Los Angeles in 2009 as Johnson was taping "Dancing With the Stars."
Johnson testified she was so afraid of O'Ryan she thought about quitting the popular TV dancing competition that she eventually won.
"He was a stranger to me. To see somebody had that much kind of obsession, it made me really scared," she said.