Carlos Lehder, a Colombian billionaire accused of being one of the world's top cocaine dealers, goes on trial today under heavy security in Jacksonville, Fla.

Lehder was arrested and quickly flown to the United States after a Feb. 4 shootout at his jungle hideout near Medellin, Colombia. He is charged in a 12-count federal indictment with exporting more than three tons of cocaine to the United States and operating a continuing criminal enterprise. He faces a maximum penalty of life plus 165 years in this case and additional federal drug charges in Miami.

Lehder, 38, has been described by law enforcement sources as a bizarre and flamboyant character, even in a world characterized by extreme behavior. He is accused of being one of the leaders of the Medellin Cartel, which is believed to handle 80 percent of the world's cocaine trade.

The sources say that in the late 1970s Lehder purchased the Bahamian island of Norman's Cay as a base for his drug empire. There he built a 3,300-foot runway that is protected by radar, armed traffickers and attack dogs. While he lived there, investigators said, Lehder maintained a yacht, 19 cars and a private disco.

The sources said Lehder describes himself as an admirer of Adolf Hitler as well as some left-wing revolutionary groups. In 1985, while a fugitive, he appeared in a television interview filmed in a jungle clearing and urged Colombian revolutionary groups to participate in the "cocaine bonanza . . . the arm of the struggle against America."

The Colombian government turned over Lehder last February as part of a crackdown after a number of the country's senior justices had been murdered by drug traffickers. But the Colombian Supreme Court last June declared the extradition treaty between the two countries unconstitutional, and U.S. sources say they believe Colombian officials are now afraid to move against the traffickers.

U.S. drug enforcement officials say the Medellin Cartel seems to have recovered completely from the loss of Lehder.

The U.S. drug enforcement sources say that Lehder -- worried about his upcoming trial -- offered last summer to cooperate with authorities. But when agents from the Drug Enforcement Administration were sent to question him, they discovered that his information has become outdated. "He didn't know anything {DEA} didn't already know," said one source.

The U.S. Marshals Service will say only that security for the trial will be "adequate." Because of complaints by defense lawyers that a heavy show of security would be prejudicial to Lehder, the marshals have agreed that security will be less obvious than at earlier hearings when guards wore bulletproof vests and carried automatic weapons.

Justice Department sources say the main witness against Lehder will be Edward Hayes Ward, whom they describe as a long-time cocaine dealer who worked for Lehder as a drug pilot starting in mid-1978. Ward was imprisoned from 1981 to 1985 on related drug charges and is now in the federal witness protection program.

Another witness will be Norman Saunders, former chief minister of the Turks and Caicos Islands, who was indicted on drug charges in 1985. Saunders, the first head of state charged with violating U.S. drug laws, was detained as a material witness in August, after he was released from a federal prison in Texas. He had served two years of an eight-year sentence.

Saunders is expected to testify that he gave Lehder and his workers overnight accommodations on his islands, situated south of the Bahamas, and that he supplied 800 pounds of marijuana to Jacksonville-based traffickers, including some who worked for Lehder.

Justice Department sources say the trial is expected to last nearly four months, with the first week devoted to jury selection.

Defense lawyers Ed Shohat and John Quinones have argued that it would be impossible to select a fair jury in Jacksonville because of extensive publicity about the case.

U.S. District Court Judge Howell W. Melton has refused to move the trial, but has said that after jury selection starts, defense attorneys can file a motion to move the trial if the jury pool appears to be strongly prejudiced.

Last month Melton denied a request by U.S. Attorney Robert Merkle to keep secret the names of the jurors. Merkle had said he worries that jurors might fear reprisals. Melton said the lawyers and defendants will be told the names of the jurors, but the jury members will be identified publicly only by number.