Attorneys for Ronald L. Humphrey, the U.S. Information Agency employe accused of spying for Vietnam, asked the U.S. District Court in Alexandria yesterday to order that a lie-detector test be administered to their client.

They said they made the request on the basis of their own sodium penothal "truth serum" examination of their client, conducted in the presence of three psychiatrists on April 3.

While under the influence of the drug Humphrey said he had no reason to suspect that his co-defendant, former Vietnamese antiwar activist David Truong, may have been working as an agent for the Socialist Republic of Vietnam, according to the motion filed in court yesterday.

Humphrey never intended to engage in espionage, according to the motion, and never gave Truong "any documents classified 'secret' or any documents that concerned national security or national defense."

At least three documents listed in government inventories of papers transmitted to Truong are classified "secret," including two listed in the original indictments returned Jan. 3 and one from the Defense Intelligence Agency whose title has not even been disclosed.

Attorney General Griffin B. Bell has said in court that the case against Truong and Humphrey is an ongoing investigation of an espionage network. The Humphrey motion yesterday oeft open the question of whether there may have been other, sources for the documents that were passed to the Vietnamese by an FBI-CIA double agent acting as Truong's courier.

The defense motion did not deny the government's charges that Humphrey passed "confidential" cables to Truong.

The original indictments against Humphrey and Truong were replaced by new ones obtained from a federal grand jury last month to correct that the prosecution viewed as defects in the original ones. All the documents listed in the new indictments are described as classified "confidential."

The government has reserved the right, however, to introduce other documents as evidence.