May 6, 1985

A lawyer who defended a Salvadoran national guardsman convicted of murdering four American churchwomen said yesterday that he had been forced to take part in a ''conspiracy'' aimed at preventing higher-ranking military officers from being implicated in the case. The lawyer, Salvador Antonio Ibarra, said that another defense lawyer had pressed him not to contradict a statement that ''the possibility of a cover-up had been thoroughly investigated'' and rejected. Mr. Ibarra said that declaration was ''an outright lie'' and added that he was specifically warned not to pursue the case on his own. After it became clear he would not cooperate fully in the plan, Mr. Ibarra said in an interview, he was abducted by Salvadoran security forces, held prisoner at National Guard headquarters and tortured. The objective, he said, was to get him off the case, either by killing him or forcing him to flee the country.

The battered old green car pulls up outside P.S. 29, an elementary school in the Cobble Hill section of Brooklyn. Out jumps a tall, handsome man in blue cotton pants and running shoes, all grace and exuberance in the morning. Jacques d'Amboise, the legendary principal dancer with the New York City Ballet who has been reborn as the Pied Piper of dance, has arrived. The children of P.S. 29 know him as Jacques - ''that man who dances,'' as Nicole Gonzalez, a kindergartener, describes him. When he bounds through the door, it is as if an electric current had passed through the corridors and classrooms: Jacques's here! Everyone from the security guard at the front door to the women serving lunch in the cafeteria starts smiling.

The seven astronauts aboard the space shuttle Challenger ended experiments today and stowed equipment in preparation for their scheduled landing here Monday at the end of what has been hailed as a highly successful seven-day mission. The Challenger is due to swoop in from the South Pacific, rake Los Angeles with a sonic boom from 90,000 feet and alight on the dry lake bed of the Mojave Desert here shortly after 9 A.M. (noon, Eastern daylight time). The landing was originally scheduled to take place at Cape Canaveral, Fla., but the hard landing of the Discovery spacecraft there last month, which damaged that shuttle's brakes, blew one of its four main tires and seriously frayed the other three, led officials of the National Aeronautics and Space Administration to switch sites as a precaution. Reason for Switching Sites With the Spacelab scientific laboratory nestled in its cargo bay, the Challenger is 12 tons heavier than the Discovery, and the almost endless dry lake beds here provide more flexibility in case of trouble.

An article in Business Day on Thursday about the Unocal Corporation misstated the personal tax impact on the company's management and directors from a possible enlargement of an offer to buy back shares. By increasing the number of shares it is offering to acquire, Unocal could not minimize the taxes they would have to pay on stock profits.

Dale Berra considered it a routine play, just a basic part of the game that he learned in high school and took with him to the big leagues. But to Billy Martin, it was a revival of Yankee tradition. Berra's aggressive slide into second base yesterday prevented a double play and kept alive the fifth inning for the Yankees. The inning ended with three runs on back-to-back homers by Rickey Henderson and Don Mattingly that helped the Yankees to a 6-2 victory over the Kansas City Royals.