MEXICO CITY, JULY 15 -- The trial in Los Angeles of four men accused of involvement in the 1985 murder of a U.S. narcotics agent has brought to the surface years of resentment by Drug Enforcement Administration officials of the Central Intelligence Agency's long collaboration with a former Mexican secret police unit that was heavily involved in drug trafficking.

According to Drug Enforcement Administration (DEA) sources and documents, the Mexican drug-trafficking cartel that kidnapped, tortured and murdered DEA agent Enrique Camarena in the central city of Guadalajara in February 1985 operated until then with virtual impunity -- not only because it was in league with Mexico's powerful Federal Security Directorate (DFS), but because it believed its activities were secretly sanctioned by the CIA.

Whether or not this was the case, DEA and Mexican officials interviewed for this article said that at a minimum, the CIA had turned a blind eye to a burgeoning drug trade in cultivating its relationship with the DFS and pursuing what it regarded as other U.S. national security interests in Mexico and Central America.

"The CIA didn't give a damn about anything but Cuba and the Soviets," said James Kuykendall, a DEA agent -- now retired -- who worked with Camarena in Guadalajara. "Indirectly, they {the CIA} have got to share some of the blame" for DFS excesses. The CIA "protected that agency for so long. They didn't want their connection with the DFS to ever go away, and the DFS just got out of hand."

A spokesman for President Carlos Salinas de Gortari expressed concern that a "fight" between the DEA and CIA -- arising from the current trial -- was dragging Mexico through the mud.

The CIA connection remains one of the murkier aspects of a case that has bedeviled two Mexican administrations. The murder continues to strain U.S.-Mexican relations, despite close cooperation by the Salinas government with U.S. anti-drug efforts and record seizures in Mexico in the last 18 months of narcotics destined for the United States.

Behind the case lies a tangled web of allegations about the CIA's special relationship with an increasingly corrupt and brutal DFS, clandestine aid for Nicaragua's contra rebels, gunrunning through Mexico and the involvement of shadowy Americans in the Guadalajara drug cartel.

Besides the battered corpses of Camarena and his Mexican pilot, Alfredo Zavala Avelares, who was tortured and killed at the same time as Camarena, the case also has left a trail of bodies -- murder victims whose deaths have received little attention.

More than a dozen persons connected to the Camarena case have been killed in mysterious circumstances in Mexico since 1985, including three of the 19 defendants in the latest U.S. indictment and several former key police commanders.

Others have been jailed on unrelated charges, effectively silencing them. Some DEA sources see these developments as part of a continuing coverup of complicity in the case, which they say reaches into the upper echelons of Mexico's government and power structure.

The DFS, an elite agency founded in 1946 under the powerful interior ministry known in Mexico as Gobernacion, cooperated with the CIA for years in monitoring Soviet, Cuban and other East Bloc agents and diplomats in Mexico, according to former CIA agents and Mexican officials.

CIA protectiveness of the DFS surfaced publicly in 1981, when the chief of the Mexican agency at that time, Miguel Nazar Haro, was indicted in San Diego on charges of involvement in a massive cross-border car-theft ring. The FBI office at the U.S. Embassy here cabled strong protests, calling Nazar Haro an "essential contact for CIA station Mexico City."

San Diego U.S. Attorney William Kennedy disclosed in 1982 that the CIA was trying to block the case against Nazar Haro on grounds that he was a vital intelligence source in Mexico and Central America. Kennedy was subsequently fired by President Reagan. At the time, Nazar Haro also was heavily involved in drug trafficking, witnesses in two U.S. trials have testified.

By the early 1980s, the DFS also had gained a reputation as practically a full-time partner of the Mexican drug lords. In 1985, after the Camarena murder, the government disbanded it in an effort to root out corruption and repair Mexico's image. But many former DFS agents remain active, especially in the Mexico City police department.

Currently being tried in a Los Angeles federal court on charges of involvement in the Camarena murder are convicted Honduran drug trafficker Juan Ramon Matta Ballesteros and three Mexicans, including Ruben Zuno Arce, the brother-in-law of former Mexican president Luis Echeverria and an alleged protector of the Guadalajara drug cartel. The jury is to begin deliberations Monday. Three other Mexicans were convicted of involvement in the Camarena murder in an earlier trial.

Seven men named in the latest indictment are currently in jail in Mexico. They include renowned drug kingpins Rafael Caro Quintero, Ernesto Fonseca and Miguel Angel Felix Gallardo, former Guadalajara secret police commander Sergio Espino Verdin and former top Federal Judicial Police officer Miguel Aldana. Caro Quintero, Fonseca and Espino Verdin have been convicted here of involvement in the Camarena murder, while Felix Gallardo and Aldana are being held on unrelated drug charges.

One of the most controversial witnesses in Los Angeles has been Lawrence Victor Harrison, 45, an American who testified that he installed communications equipment, including electronic eavesdropping devices, for both the DFS and the Guadalajara drug cartel in the early 1980s.

His allegations, in testimony and DEA documents, of gunrunning and guerrilla training in Mexico and the involvement of top government, police and military officials in crimes ranging from drug trafficking to murder, have prompted angry denials from the Mexican government.

For U.S. law enforcement, especially frustrating has been the role of a potential witness who vanished before the trial, a 47-year-old former police official in Mexico named Sergio Saavedra Flores. He is suspected by the DEA of involvement in the Camarena murder coverup.

According to a senior DEA official familiar with the Camarena investigation, the CIA had infiltrated the Mexican drug organizations. "Of course they have. They look at it from the standpoint that narcotics is {related to} national security."

"The traffickers were monitoring the DEA, and the CIA knew about it but didn't tell us," he added angrily. "They {the traffickers} knew everything we were doing. The only thing they didn't know was the information we had on corruption." As proof of the monitoring, after the murder the DEA received a voice-activated tape recording of DEA radio communications that Mexican authorities said was seized from the traffickers.

Angered by heavy losses in DEA-instigated raids on huge marijuana plantations, the Guadalajara cartel kidnapped Camarena to interrogate him on what the DEA knew about the traffickers' operation and high-level Mexican corruption, DEA officials have said.

The CIA declined as a matter of policy to address whether it had any relationship with specific persons, or address questions about drug and arms trafficking in Mexico.

CIA spokesman Mark Mansfield would say only, "I want to emphasize in the strongest possible terms that the CIA neither engages in nor condones drug trafficking. Nor did we participate in any coverup of the Camarena case."

The senior DEA official said Saavedra is a Cuban who came to Mexico and rose to a high position in the DFS. Under the administration of Salinas's predecessor, Miguel de la Madrid, he became a special assistant to Manuel Ibarra, then director of the Federal Judicial Police. Ibarra was indicted in Los Angeles in January in the Camarena case and has dropped out of sight.

After the DEA complained that Mexican investigators were treating Caro Quintero with kid gloves following his arrest in April 1985, Saavedra was brought in for interrogation. A police source who witnessed the scene said the drug lord was tortured by various means, including spraying carbonated water up the nose. "We almost lost him a couple times," he said.

By this account, Caro Quintero gave up the names of top military and police officials he was paying off, including the head of the DFS, Jose Antonio Zorrilla Perez, a protege of the interior secretary at the time, Manuel Bartlett.

Alarmed that the DEA investigation was pointing to top Mexican officials, Saavedra then joined the coverup, helping Matta Ballesteros, the Honduran, to flee Mexico, the DEA official said. Zorrilla was arrested a year ago on charges of ordering the murder of a Mexican investigative journalist in 1984.

"Saavedra got scared because he felt the rules of the game had changed," the official said. The investigation "was no longer contained. . . . Now we were attacking the DFS. The gringos were going beyond the bounds of looking at the traffickers."

Saavedra left Mexico and took a job in Los Angeles in 1987 with the U.S. subsidiary of Mexico's pro-government private television network, Televisa. When the DEA contacted him last November about cooperating in the Camarena case, he abruptly quit his job, packed up his family and moved out of his Orange County home.

"He just disappeared," a friend in Los Angeles said. Asked why, she said, "We related it to Camarena."

Colleagues at the television company said Saavedra claimed to come from Veracruz, a port on the Gulf of Mexico where customs and accents are similar to Cuba's.

Saavedra's name appears on a list prepared by the U.S. attorney's office in Los Angeles of persons linked to the Camarena case. But the chief government prosecutor, Manuel Medrano, refused all comment on Saavedra.

Certainly, only a part of the Camarena story has emerged from the courts. Judges in both trials rejected defense lawyers' attempts to introduce evidence about alleged links between the CIA and Felix Gallardo.

In June, U.S. District Judge Edward Rafeedie barred defense lawyers from questioning Harrison about the CIA, but relented this month after ordering the prosecution to give the defense two secret DEA summaries of Harrison's statements on the subject.

Testifying in the absence of the jury July 6, Harrison said Felix Gallardo had told him personally that he thought his drug trafficking network was secure because he was supplying arms to the U.S.-backed contras. Harrison quoted the drug lord as saying he had persuaded unspecified other people to fund the Nicaraguan rebels.

Harrison said he had no direct knowledge of CIA involvement with the traffickers but believed that contras had been trained in Mexico. He said the DEA had misquoted him in a February report as having said that the CIA, using the DFS as cover, had trained leftist Guatemalan guerrillas on a Mexican drug lord's ranch.

Rafeedie criticized Harrison's testimony as "based on hearsay, gossip and speculation." The judge did not allow the jury to hear that testimony.

Last month, Harrison, who said he was born George Marshall Leyvas in 1944, testified that he had audited classes under two assumed names during the late 1960s at the University of California at Berkeley and joined the leftist anti-Vietnam war group, Students for a Democratic Society.

Harrison said that after moving to Guadalajara in 1971 and working as a law clerk for a Mexican attorney, he served as a lawyer for a branch of the ruling Institutional Revolutionary Party and defended leftist university students accused of subversion.

After these activities led to his arrest by the DFS, he said, he offered electronics services to the DFS and other police agencies in Guadalajara. He said he had had "no formal training" in electronics, which was "just a hobby."

Between 1981 and 1984, he said, he installed sophisticated radio communications systems for the DFS and a secretive sister agency under the Interior Ministry known as the Department of Political and Social Investigations, or IPS. Senior DFS and IPS commanders soon introduced him to the drug lords who operated in partnership with these police agencies, he said.

On orders from the police commanders, Harrison said he set up communications systems for drug lords Fonseca and Caro Quintero and moved into Fonseca's house from July 1983 to January 1984.

"As the system engineer, I listened to the system and had full control of it 24 hours a day during the entire time that it was installed and operated," Harrison testified.

He said he overheard thousands of conversations among traffickers and their police partners by both monitoring the drug lords' radios and tapping their telephones.

Harrison also installed a device to monitor the DEA's radio communications in Guadalajara, he said, but did not tap the agency's phones -- a job he indicated was done by someone else from the Interior Ministry.

The 6-foot-7 Californian, who was nicknamed "Torre Blanca" (White Tower) by his Mexican cohorts, said that after he completed work on Fonseca's system around September 1984, he was shot nine times in an ambush by rival state police, effectively ending his career with the traffickers. While he was hospitalized in a prison infirmary, Camarena was killed and both Caro Quintero and Fonseca were arrested.

Describing a series of large arms seizures in Mexico around that time, including cases of AK-47 assault rifles, the senior DEA official said that at first, "we thought it was for the traffickers. Naive us. We thought, my God, they're arming the whole damn country."

A former U.S. drug trafficker and gunrunner who turned government informant in a separate case said in an interview that he smuggled weapons to Mexico for delivery not only to traffickers but to various guerrilla groups in Central and South America. In the interview, he also confirmed that Harrison had worked for Fonseca and lived in his house.

"The CIA obviously was cultivating a very powerful and efficient arms transport network through the cartel, and they didn't want DEA screwing it up," Gregory Nicolaysen, one of the defense lawyers in the trial, said outside the court.

Nicolaysen said that Harrison "basically was the liaison between the agency and the cartel." Aside from certain "embellishments," he said, "Harrison does have a fair amount of credibility." Harrison has denied in court that he ever worked for any U.S. government agency.

The lanky American testified that he left Mexico permanently in February because of death threats. He is currently a paid informant of the DEA.

Starting around six months before Camarena was killed, which coincides with the time that Harrison said he finished installing the traffickers' communications, the DEA lost several informants in Guadalajara, DEA sources said. Among those that Camarena called most frequently, court testimony indicated, was his pilot, Zavala.

In a DEA debriefing last Sept. 20, a transcript of which was given to defense attorneys at the start of the trial, Harrison said Fonseca had told him in 1983 that "there couldn't be any trouble with the Americans because they {the traffickers} were together with the Americans. . . . There was some kind of a secret understanding."

Harrison added that Javier Barba Hernandez, another member of the Guadalajara cartel who was killed by federal police in December 1986, "told me that it was a political thing that I shouldn't get involved in."

Among several foreigners who visited Fonseca, apparently to discuss drug deals, were two Americans who said they were "working with the contras," Harrison said. He said that when he warned one of the men against flying too close to the U.S.-Mexican border because of U.S. radar, "he said he was the U.S., that he didn't have any problem."

Sometime in 1984, the DEA transcript quoted him as saying, he realized that Fonseca was "mad at the Americans." He added, "I got the feeling that he felt betrayed."

A report attached to the transcript said Harrison identified Theodore Cash, a former CIA pilot, as an American who flew guns and drugs for the Guadalajara cartel. Cash acknowledged that he had flown for the CIA for 10 years when he testified in the previous Camarena trial under a grant of partial immunity.

According to a secret DEA report of a Sept. 11, 1989, interview with Harrison, another American, who identified himself only as "Dale," arranged a meeting with Harrison in Guadalajara in 1987 and asked him "what information {he} had supplied to DEA concerning CIA operations in Mexico."

Harrison said "Dale" told him he was "not DEA" and worked at the U.S. Embassy in Mexico City, the report said. Taking "Dale" for a CIA agent, Harrison "stated that you guys {CIA} are working with the traffickers in Mexico. We {Gobernacion and the Mexican intelligence community} know that the CIA are supplying guns to Nicaragua," the report said. In response, it said, " 'Dale' nodded his head in an affirmative manner."

Defense lawyers said the report's description of the American matched that of Dale Stinson, a DEA agent now based in Phoenix who had testified earlier on a separate matter. Reached in Phoenix, Stinson declined all comment.

Antonio Garate Bustamante, 51, a former high-ranking Guadalajara police officer who became a DEA operative after the Camarena murder, orchestrated the abduction in April of a Guadalajara doctor wanted in the Camarena case. He said several potential Mexican witnesses had died mysteriously, landed in jail or disappeared since he began trying to recruit them on behalf of DEA investigators.

He also said that former Federal Judicial Police major Aldana, indicted in Los Angeles in January, had agreed to cooperate, but was arrested in Mexico on drug-possession charges three days after their last phone conversation.

Garate said at least three others sought by the DEA were gunned down by Mexican police.

"They didn't want us to have anybody alive," he said.