A federal judge sentenced the chemist who created "the Clear," the undetectable designer drug at the heart of the BALCO steroid scandal, to three months in prison and three months of house arrest today on a charge of conspiring to distribute steroids. Patrick Arnold, 40, an executive with a nutritional supplements laboratory in Champaign, Ill. has until Sept. 19 to begin serving his sentence, U.S. District Judge Susan Illston said at a hearing in San Francisco. "It's a really destructive path you've been on, and a very serious crime you've committed," the judge told Arnold.