Parents Patsy Ramsey, who died in 2006, and John Ramsey had been the target of intense media speculation, fueled by police leaks, since the child beauty queen was killed in her home.
Boulder District Attorney Mary Lacy, in a letter to John Ramsey, said "We do not consider your immediate family, including you, John, your wife, Patsy, and your son, Burke Ramsey, to be under any suspicion in the commission of this crime," NBC affiliate KUSA-TV, Denver, reported.
"The suspicions about the Ramseys in this case created an ongoing living hell for the Ramsey family and their friends, which added to their suffering from the unexplained and devastating loss of JonBenet," Lacy said.
John Ramsey said in an interview with KUSA he was "grateful that they acknowledge that we, based on that, certainly could not have been involved."
Patsy's sister, Pam Paugh, told the broadcaster the prosecutor's letter means "we have a killer on the loose. That killer remains at large."
The report said the prosecutor's decision was based on the results of new DNA samples tested at Bode Technology Group in Lorton, Va., with "touch" analysis, not available in 1996.