Auto maker John Z. De Lorean's co-defendant in an alleged multimillion-dollar cocaine smuggling case pleaded guilty today and agreed to testify against De Lorean in return for reduced criminal charges and the possibility of a shorter prison term.

The guilty plea on six federal drug charges by pilot-inventor William Morgan Hetrick came less than two months before the cases of De Lorean and a third co-defendant, former Hetrick aide Stephen Lee Arrington, are scheduled to go to trial. De Lorean attorney Howard Weitzman indicated that he would seek a delay in the Aug. 9 trial date to probe Hetrick's background, but said he did not think Hetrick's testimony could hurt his client.

"Mr. Hetrick came into this after the government lured John in," said Weitzman, who watched Hetrick change his earlier "not guilty" plea before U.S. District Court Judge Robert M. Takasugi.

Prosecutors have charged that De Lorean tried to raise funds for his faltering sports car firm by offering to finance shipments of cocaine and heroin that Hetrick was to fly into the country.

Undercover agents and a key government informer were involved in the deal from the beginning; De Lorean has charged they forced him to participate by cutting off legitimate sources of funds for his company and threatening the lives of his children.

Court documents released today show that Hetrick agreed to cooperate with the government on Feb. 24, but the formal proceeding was delayed until federal agents could secure from a Cayman Islands bank $448,93l.79 in what prosecutors said were Hetrick's illegal drug profits.

Under a government plea agreement, prosecutors dropped one count against Hetrick of possession of $6.5 million worth of cocaine with intent to distribute and one count of conducting "a continuing criminal enterprise." The latter is the most serious drug violation in federal law, carrying a minimum 10-year prison term and a maximum life sentence.

Hetrick agreed to plead guilty to two new charges, one count of income tax evasion and one count of illegal currency transportation.

Takasugi set sentencing for after the De Lorean trial, and attorneys said Hetrick's sentence could be considerably reduced if his cooperation was useful in convicting De Lorean and leading investigators to other drug operations.

Hetrick was an acquaintance of James T. Hoffman, an aircraft salesman and convicted drug trafficker and the key government informer in the case against De Lorean. Hoffman was once a neighbor of De Lorean in San Diego County and has told prosecutors that De Lorean approached him seeking a drug deal.

De Lorean, however, has suggested that Hoffman tried to lure him into the deal and his attorneys have asked the government for wide-ranging information about Hoffman's background. Today, Weitzman suggested a further link between Hetrick and Hoffman, saying that Hetrick attorney Stephen Wilson once represented a drug dealer who helped federal agents track down Hoffman.