Although a majority of Americans say they closely follow the daily turns of the O.J. Simpson murder trial - including a “hard core” of nearly one in four who seems obsessed - the number of people across the nation watching television news shows or reading newspapers continues to decline, according to a poll released today by a media monitoring group.

The Times Mirror Center for the People and the Press estimated - based on its survey results - that about 40 million people, or about 24 percent of the adult public, are watching “all or most” of the daily live O.J. Simpson coverage, while about 59 percent “watched, read or heard” about the trial coverage.

Nevertheless, the study found, network broadcast news viewing is down to 48 percent from the 60 percent who said they watched the news “regularly” in May 1993. Regular local television viewing dropped less dramatically during the same period to 72 percent from 77 percent of those polled.

And respondents report diminishing patience with newspapers. Forty-five percent reported reading a newspaper “yesterday,” down compared with the center’s findings in February 1994 (58 percent), in January 1994 (49 percent) and in March 1991 (56 percent).