ANNAPOLIS, JULY 16 -- An Anne Arundel County grand jury voted today not to indict two former National Security Agency psychologists whose son ran a drug ring out of their Crofton home.

"The grand jury felt that the {police} investigation was exhaustive, and for better or for worse there simply was insufficent evidence on which to base an indictment," vice foreman Anne Kennedy said of the case against Air Force Lt. Col. Russell J. Hibler and Suzanne McCabe Hibler. "I would not say they were cleared," she added.

The Hiblers' son, James Todd Hibler, 22, has pleaded guilty to drug distribution charges. Jessica Lynn Hibler pleaded guilty in May to a misdemeanor stemming from helping her brother count his drug money. Both are awaiting sentencng.

Reached at home today, Suzanne Hibler declined to comment on the grand jury's action.

The parents' role in Todd Hibler's drug-trafficking ring, one of the largest in county history, has been a subject of intense speculation here since police raided their home Nov. 2 and discovered two pounds of marijuana, $15,000 in cash and a boxed AK-47 assault rifle in common areas of the residence.

Police also found large quantities of marijuana and cocaine in Todd Hibler's locked bedroom and said the entire house smelled of marijuana. The parents were arrested and charged with narcotics distribution. Those charges were dropped in January while the investigation continued.

Today, Lt. Gary Lyle, chief of the police narcotics section, said his investigators had been unable to find a single witness implicating the elder Hiblers during an eight-month investigation.

"Of the 50 or so witnesses we interviewed, no one could point to Mom or Dad as having any involvement," Lyle said. "People were classifying the parents as naive or stupid . . . but we didn't have anyone indicate they even knew the drugs were in the house or saw any of the transactions."

Meanwhile, the Air Force has requested the county's records and is investigating Russell Hibler, an Air Force spokesman said.

Sources said neither Hibler has worked at NSA since being arrested.