An independent attorney's probe of charges that antigovernment rebels in Nicaragua commit human rights atrocities has produced 145 sworn affidavits from witnesses that he claims document "a distinct pattern" of murders, kidnapings, assaults and torture of civilians.

The report by Reed Brody, 31, a former assistant state attorney general in New York, is to be released at a news conference today by the International Human Rights Law Group and the Washington Office on Latin America (WOLA), private groups that endorse the findings. A copy was provided to The Washington Post.

Rep. Samuel Gejdenson (D-Conn.), who is also scheduled to attend the news conference, said yesterday that the House Foreign Affairs subcommittee on the Western Hemisphere, of which he is a member, will review the report to check its accuracy.

"It's clear we have a situation where the 'contra' [rebel] targets are primarily and almost exclusively civilians," he said. If Congress provides $14 million in additional aid to the rebels that the Reagan administration has requested, he said, "we become knowing accomplices to the crimes of the contras."

The report is the latest in an escalating crossfire of studies, testimony and speechmaking by both the Reagan administration and its critics over the future of the three-year-old program of U.S. aid to rebel groups fighting the leftist Sandinista government of Nicaragua. The issue is scheduled for congressional debate next month.

Brody's report is the first to include sworn affidavits from witnesses who he said are available for further questioning.

Brody said in an interview that he began the study after visiting Nicaragua last summer with an office colleague whose brother is a priest there. Moved by residents' accounts of contra attacks, he said, he was receptive when Paul Reichler, Nicaragua's attorney in Washington, suggested a serious probe of the charges "as if taking evidence for a court case."

Brody said he quit his job of four years and spent about $1,800 of his own money to go to Nicaragua and conduct the study between Sept. 14, 1984, and Jan. 13, 1985.

Brody said he wrote the 141-page report and approached WOLA -- known as a critic of administration policy -- which joined the International Human Rights Law Group in sending two other attorneys to Nicaragua to recheck Brody's findings.

The two are New York attorney Donald T. Fox, vice president of the International Commission of Jurists, and Michael J. Glennon, former counsel to the Senate Foreign Relations Committee. In a joint statement, they said "the preponderance of the evidence indicates that the contras are committing serious abuses against civilians" and that Brody's report appears accurate.