Charles V. Harrelson is a gambler and, like many gamblers, he likes to brag. Killing people and getting away with it was his long suit, he once told an acquaintance.

The acquaintance has since repeated that boast, showing Harrelson tends to exaggerate, in a federal courtroom here. The record shows Harrelson was acquitted of killing a man in May, 1968, but also that two months later he was accused of killing another man for $1,500. He was convicted in that slaying and sentenced to 15 years.

Today Harrelson, 44, spends his days in the circular courthouse in San Antonio that bears the name of U.S. District Court Judge John H. Wood Jr. Government lawyers say Harrelson killed Wood with a high-powered rifle on May 29, 1979.

The government spent nearly $5 million investigating the murder of Wood, who had earned the nickname "Maximum John" for his stiff sentences in drug cases. Wood was the first federal judge assassinated in this century, and the investigation that followed was the largest since President Kennedy's assassination. The government made it a top priority as part of its war against drug peddlers.

But for many months, the case was an embarrassment to the government because federal agents could not track down the killer or killers. To obtain evidence, the government made extensive use of wiretaps, surreptitious tape recordings and informers. Defense attorneys, saying the government bent the law to obtain evidence, challenged its admissibility.

Last April, a federal grand jury indicted five persons in connection with the crime. Federal prosecutors said Harrelson was paid $250,000 by Jamiel (Jimmy) Chagra, 38, of El Paso, to gun down Wood outside his San Antonio town house.

At the time, Chagra was facing drug charges before Wood. Chagra later was convicted of those charges and is now serving a 30-year sentence.

Chagra and Harrelson are charged with murder in the Wood case. Government lawyers said the consipiracy to kill the judge and obstruct the investigation also included Chagra's younger brother, Joseph, 35, a lawyer; Jimmy Chagra's wife, Elizabeth, 28; and Harrelson's wife, Jo Ann, 43.

Harrelson, his wife and Elizabeth Chagra are being tried together. Jimmy Chagra will be tried separately later. Joe Chagra struck a deal with the government and was given a 10-year sentence in return for his testimony. But he will not be forced to testify against his brother, whom he called "a bombastic liar" on the witness stand recently.

The trial enters its ninth week Monday. Government lawyers wrapped up the prosecution a week ago after calling more than 80 witnesses. In the final hour of Friday's session, Harrelson, dressed in a three-piece denim suit, took the stand in his own defense.

His lawyer, Thomas G. Sharpe Jr., said Harrelson was in Dallas at the time of the killing. He also said Harrelson earned a good income from gambling and didn't need the money for killing the judge.

Sharpe hopes to have Harrelson demonstrate his abilities as a "card mechanic" in the courtroom this week. But it is not clear that the request will be granted by Judge William S. Sessions, a friend of the slain Wood, who rejected a motion that he step down from the case.

The government built its intricate case against the three defendants on circumstantial evidence because there was no eyewitness to the killing. Joe Chagra, who once served as an attorney for Harrelson and his brother Jimmy, testified Harrelson had told him he killed Wood "with a clean shot." Another witness put Harrelson at Wood's town-house complex shortly before the murder.

Three witnesses for the defense say Harrelson was in Dallas later that morning.

Jo Ann Harrelson already has been convicted of illegally purchasing a weapon that prosecutors say is the same type of rifle that was used to kill the judge. The murder weapon has never been found, although the stock of a rifle like that used in the killing was uncovered near an area Harrelson had described to Joe Chagra in a crudely drawn map.

Jo Ann's daughter, Teresa Starr, testified that she had been sent by her mother and stepfather Harrelson to Las Vegas a month after Wood's death to pick up $250,000. Prosecutors say she got the money from Elizabeth Chagra. Teresa Starr also told the court she had been urged by her mother and Harrelson to keep the trip "a secret to my grave." She also admitted having had an affair with Harrelson.

Elizabeth Chagra has become a born-again Christian while in federal custody. Shortly before the trial opened, she wrote a letter to Wood's widow.

"I am a newly born Christian and after making my peace with God . . . . You may choose to never forgive me for my involvement and I would truly understand," she wrote.

Asked by a government lawyer how she felt about Elizabeth Chagra, Wood's widow replied, "I feel she has found Christ too late."

Prosecutors also brought in witnesses who said they knew Harrelson. One said Harrelson made the remark about killing and getting away with it shortly after Wood's death. He also said Harrelson said Wood "had committed suicide" with his stiff sentences.

Another government witness said Harrelson had once indicated that he saw the human head as just "a watermelon with hair."

Harrelson, already serving a 40-year sentence on drug and gun charges, was somber when he took the stand Friday. Ironically, he told the jury he once let law enforcement officers in California put a transmitter on him to tape the conversations of a man charged with murder. Harrelson, who was facing robbery charges, later testified against the man.

He described a succession of jobs in the dental supply business, several marriages, multiple addresses and various name changes.

Asked his occupation, he replied, "gambler," and said he had started at age 12. Asked his occupation in jail, Harrelson smiled at the jury and, alluding to the government's bugging of his cell, said, "Making tapes for the government."