Police here are trying to solve a spectacular slaying that has sent shock waves through Venezuelan political circles.

The victim was a lawyer investigating a delicate matter -- alleged multimillion-dollar corruption among the nation's military. His killing, which some have linked to the armed forces, could complicate relations between the government and the nation's traditionally apolitical military.

The lawyer, Juan Luis Ibarra Riverol, a retired Air Force major, former minor presidential candidate and a believer in astrology, was found dead in his office two weeks ago with a bullet through his mouth and another through his head.

Ibarra was acting as attorney for Lt. Col. Luis Alfonzo Godoy, who has accused retired generals Tomas Abreu Rescaniere, Vicente Luis Narvaez Churion and Bernardo Leal Puchi -- all defense ministers in governments of former president Luis Herrera Campins -- of irregularities in military procurement contracts resulting in overpayment by $70 million.

At least two National Guard sergeants -- one retired, the other in active service -- have been detained so far. Other suspects are reported to have links to military intelligence.

While the government has kept silent on the progress of the investigation, conflicting stories, inflammatory accusations and widespread speculation have filled the vacuum.

A leading daily, El Diario de Caracas, has advanced a potentially explosive theory for the killing. According to El Diario, Ibarra was the first victim of a plot to destabilize the government, allegedly devised by a former head of military intelligence, Gen. Rafael Arturo Machado Santana, who is wanted on charges of corruption and is now living abroad.

El Diario said Machado planned to use drug money to kill a number of important politicians and government officials in an attempt to provoke a right-wing coup. Ibarra, according to El Diario, was eliminated because he had compromising documents in his possession.

Interior Minister Octavio Lepage has denied that the government is holding a number of military officers for questioning in connection with the "Machado Plan," as asserted by El Diario, but he dodged giving a direct answer when asked whether such a plan exists.

"We do not discount any hypothesis. We are working on them all," Justice Minister Jose Manzo Gonzalez, himself reportedly a target of the alleged assassination campaign, told reporters.

When his attorney's slaying was discovered, a distraught Col. Godoy accused the three former defense ministers of complicity. "The intellectual authors of the assassination of Dr. Juan Luis Ibarra Riverol are concretely the former defense ministers denounced by me and those who have taken up their cause," Godoy said.

The former defense ministers have denied any involvement in Ibarra's death.

The government has promised that the investigation of Ibarra's killing will be pursued to its ultimate consequences. The case "won't turn into a crab," said Interior Minister Lepage. The term "crab" is used here to describe an investigation that gets nowhere due to pressure from powerful groups.

Politicians from all parties have agreed that the killing, the third of a lawyer involved in a controversial case during the past four years, has cast a shadow over the workings of Venezuela's 26-year-old democracy.

Gonzalo Barrios, patriarch of the ruling Democratic Action Party, said the "suspicions" engendered by the killing have hurt the prestige of Venezuelan democracy, while leftist Sen. Pompeyo Marquez said the slaying called into question whether powerful circles could be truly investigated.

The controversy follows a series of major scandals that had undermined belief in the country's democratic and legal institutions. The charges of military corruption, and now Ibarra's death, have spread that cloud of suspicion to the armed forces, which pride themselves on their nonpolitical, professional role.

The allegations and innuendoes following Ibarra's assassination have succeeded in irritating the military. In a published interview, the Army chief of staff, Gen. Jose Antonio Olavarria, implied that the military was the victim of a smear campaign whose goal was to weaken the institution.

The armed forces are staunchly democratic, Olavarria said, and although some military men possibly have been touched by corruption, "We cannot accept that the Army be tied to or be treated as if it were a corrupt institution. We will never accept that."