An intensive 13-month investigation into the celebrated homicide of 6-year-old JonBenet Ramsey ended this afternoon when local prosecutors announced that a grand jury had completed its probe without filing any charges in the case.

The news appeared to increase the likelihood that no clear answer will ever come to the question that has gripped the nation since the young beauty queen's lifeless body was found the day after Christmas three years ago -- "Who killed JonBenet?" But authorities here will doubtless continue to investigate the killing, for which there is no statute of limitations.

"The Boulder grand jury has completed its work and will not return," Boulder District Attorney Alex Hunter told a huge crowd of reporters gathered near the city's Justice Center. "I, and my prosecution task force, believe we do not have sufficient evidence to warrant the filing of charges against anyone who has been investigated at this time."

Hunter declined to answer questions about the grand jury's work, which is secret, so it could not be determined whether prosecutors asked for a vote on an indictment.

The decision to end the grand jury's term without issuing an indictment in the slaying represents a validation of Hunter's own refusal to charge anyone during an investigation that was roundly criticized here by police authorities who pressed for an arrest. It leaves lingering questions about a homicide case that captured worldwide attention and provided constant grist for the tabloid mill from the moment JonBenet's body was discovered in the basement of her parents' home and the world came to know her as the reigning Little Miss Colorado, an artfully made-up youngster prancing across a stage in a pink cowgirl outfit.

Saying "the Ramsey family lives in a nightmare" of endless "public lynching and speculation," JonBenet's parents issued a statement tonight asking that the investigation continue. "We take no satisfaction in this result because a child killer remains free and undetected."

They may get their wish. Colorado Gov. Bill Owens (R) said he is considering taking the unusual step of giving the case to a special prosecutor.

"Everyone is disappointed with the fact that there isn't enough evidence, at this time, to indict," Owens said tonight. "As governor, I have the power to appoint a special prosecutor. I am reviewing this option and will make a decision shortly."

The grand jury's decision for now clears suspicions that JonBenet's parents, John and Patsy Ramsey, were involved in the girl's death. The couple have steadfastly maintained their innocence, despite police statements that they were under suspicion and widespread speculation that one or both of them were involved in the death of the beautiful young girl with the starlet's smile and poise.

JonBenet Ramsey's body was discovered by her father in a basement room of the family's $760,000, 15-room, Tudor style house about 1 p.m. on the day after Christmas, about seven hours after her parents reported to police that she apparently had been abducted. She had been strangled with a crude garrote made from the broken handle of a paint brush, her skull was fractured, and she showed signs of sexual abuse.

A purported ransom note asked that $118,000 be paid to a "foreign faction." Almost from the outset, JonBenet's parents -- John Ramsey, the chief executive officer of Access Graphics, a Boulder computer firm, and his wife Patsy, a former Miss West Virginia -- were considered logical suspects. Investigation commander and now Boulder Police Chief Mark Beckner said they were under "an umbrella of suspicion," a judgment reinforced by the Ramseys' initial refusal to consent to interviews with authorities and their retention of separate lawyers.

The Ramseys eventually went through two separate rounds of interviews with authorities.

"I would have given my life for JonBenet," said John Ramsey in a British television documentary.

"Absolutely not," replied Patsy Ramsey when asked if she played any role in her daughter's death.

From the very first, the case was marked by criticisms of a police force portrayed as inept, and infighting between police and Hunter, who in nearly 30 years as Boulder County prosecutor has earned a reputation as someone who is sometimes reluctant to take cases to court. "Boulder County expects people to be innovative," he told the Denver Post this year, defending his interest in alternative forms of treatment.

Boulder police at the scene of the crime were criticized for allowing the Ramseys and several friends to wander freely through the house for seven hours after they reported their child had been kidnapped. Police allowed John Ramsey and two friends to look around the house, a search that turned up JonBenet's body. That, said critics, may have fatally compromised key evidence.

Prosecutors, in turn, were criticized for being too cozy with some of the battery of lawyers hired by the Ramseys and being overly reluctant to bring charges.

At times, the Boulder law enforcement community seemed at war with itself and shattered by the case. Among the developments over nearly three years:

Police Chief Tom Koby, who had confidently predicted that "our man won't walk," resigned.

Detective Steve Thomas, one of the original investigators, alleged the prosecutor's office had "thoroughly compromised" the probe.

Sgt. Larry Mason filed a lawsuit after being removed from the investigation because of suspicions he had leaked information to reporters.

Detective Linda Arndt, criticized for lax control of the crime scene, also sued the department and Koby alleging they had violated her rights to free speech rights by preventing her from speaking out. She appeared earlier this year on "Good Morning America" and said she knows who the killer is but the "the person who killed JonBenet will not see justice as we would like to see."

Another key investigator, Lou Smit, resigned a year ago, saying the Boulder police in pursuing the Ramseys were "going in the wrong direction." He could not, said Smit, "in good conscience be part of the persecution of innocent people."

Hunter, according to a book published by Lawrence Schiller, "Perfect Murder, Perfect Town," used tabloid reporters to dig up dirt on a police commander who was the lead detective in the case.

If all that seemed like a running soap opera, the tabloids -- print and television -- treated it as one.

During the life of the case, according to Anne Imeson, research coordinator at NewsTV Corp., more than 300 reports aired on the Ramsey case on the top evening tabloid television shows and the major networks' flagship magazine shows.

In their statement tonight, the Ramseys asked that the investigation be renewed by the detectives who were removed in 1998: "This crime cannot be solved by those who close their minds to any lead which is inconsistent with their biases."

With the crime scene so compromised, the infighting among authorities, and critical unexplained evidence such as unidentified DNA found in JonBenet's underpants and under her fingernails, legal experts said it would have been extremely difficult, if not impossible, to win a conviction in the case.

"If there were an indictment for first-degree murder, it would have been virtually impossible to get a conviction," said Andrew Cohen, a Denver legal commentator who has followed the case closely. "Sometimes cases just don't get solved."

Staff researcher Nathan Abse in Washington contributed to this report.