Thomas, 41, was scheduled to plead guilty Tuesday in Prince William County Circuit Court to two charges of rape and three charges of abduction in a 2009 attack on three teenagers, but stood before Judge Mary Grace O'Brien and said, "I don't know which way is right or wrong. I'm not sure if I know what I'm doing," The Washington Post reported.
Thomas is suspected of committing at least a dozen rapes and other attacks in the Washington area and along the East Coast, investigators said, and in a newspaper interview published Sunday admitted his responsibility in the crimes.
Prince George County, Md., police have linked five rapes to Thomas, a truck driver, between 1997 and 2001, who could face additional trials in Virginia, Maryland and Connecticut where he allegedly attacked women, the newspaper said.
Declining the plea deal will likely lead to Thomas' trial in January, the newspaper said.
Prosecutor Paul Ebert, who said he had intended to drop three firearms charges against Thomas and hoped to spare victims from testifying in a trial, said he did not know why Thomas declined the arrangement.