The selection of a jury in the trial of Dr. George Nichopoulos -- charged with over-prescribing dangerous drugs to Elvis Presley -- was to be completed yesterday in Memphis, Tenn., criminal court. That jury is scheduled to hear testimony from Dr. Eric Muirhead, the pathologist who officiated at the rock star's autopsy.

Nichopoulos, a 53-year-old internal medicine specialist, is charged in a 14-count indictment with irregularities in his prescriptions to Presley and eight other patients. The charges carry penalties of two to 10 years in prison and a fine of $20,000 on each count.

The State Board of Medical Examiners suspended Nichopoulos' medical license for 90 days in 1980 following a week-long hearing. During that hearing, an attempt was made to bring Muirhead to the witness stand. His testimony was blocked by a legal technicality involving patient confidentiality -- the autospy report was sealed at the request of the Presley family.

Sandra Day O'Connor, in her first day as a working Surpreme Court justice yesterday, wasted little time in asking her first question from the high court bench.

Her question referred to California's bid to obtain an offshore oil and natural gas leasing system that would yield greater revenue for the state.

Justice O'Connor began her workday shortly before 8 a.m., arriving at the court in a compact car.

After taking the bench for her first public working session with her eight male colleagues, she watched intently the formalities and introductions that accompany the start of the court's new term.

Several times she donned a pair of eyeglasses, although she rarely has been photographed wearing them.

Sitting in the front of the courtroom was her husband, John J. O'Connor III. Sitting nearby was Potter Stewart, whose retirement as a Supreme Court justice July 3 opened the way for President Reagan to keep his campaign promise to nominate the first woman to the high court.

Actress Sophia Loren and her film producer husband Carlo Ponti have lost another battle with Italian courts, this one costing them $6.7 million in precious art works by Picasso, Braque and De Chirico, according to a ruling made public yesterday by the Italian Supreme Court in Rome.

The confiscation order is the latest move in Italy's legal skirmish with Ponti, who was convicted in absentia in January 1979 of currency smuggling through his multinational film company. At the time he was sentenced to four years in prison and fined 22 billion lire ($27 million).

Loren was at first charged along with her husband of currency fraud, but later absolved. Ponti, who lives with his wife and children in Paris, has not returned to his native Italy since his legal troubles began.

The government confiscated the works of art after Loren visited Italy in March 1977 and tried to take some of them out of the country. Judicial officials said the confiscated art works could be sold at auction or placed in a state museum.

A federal judge in New York ruled today in favor of the heirs of Groucho, Chico and Harpo Marx, saying that the production of the play, "A Day in Hollywood/A Night in the Ukraine," infringed the plaintiffs' right of publicity in the Marx Brothers characters.

The lawsuit filed in Manhattan federal court in April 1980, asking for damages to be "appropriately determined by the court," named as defendants the producers of the smash musical, Alexander Cohen and Day and Night Co. Inc., plus the Shubert Organization (which reached a stipulated settlement with all parties last February).

Richard K. Vosburgh, who wrote the book and lyrics, and Frank Lazarus, who composed the music, were brought into the suit as "third party defendants" by the producers.

The show originally opened in London in January 1979, made its U.S. debut in Baltimore in March 1980 and moved to Broadway on May 1, 1980. The show closed just last week.

The plaintiffs in the suit are Groucho Marx Productions Inc. and Susan Marx, wife of Harpo Marx.

In his 24-page decision, U.S. District Judge William Conner wrote: "Although literary commentary may have been the intent of the playwright, any such intent was substantially overshadowed in the play itself by the wholesale appropriation of the Marx Brothers characters."

Both the title and the show itself are in two parts. The first half of the production is a revue with old Hollywood standards and original songs. Conner's decision noted that the "plaintiffs take issue with the second half of the play which features performers simulating the unique appearance, style and mannerisms of the Marx brothers."