It is not clear why the 1989 case failed to turn up in the federal system, and California court officials said they did not have an explanation. But the omission highlights a frequent problem: There are major gaps in the databases, which rely primarily on accurate and complete reporting by local and state agencies.

The Justice Department has reported, for example, that states fail to transmit most of their active arrest warrants from their own databases into the federal system and often neglect to update records to show whether cases resulted in convictions. Some states still rely on paper files, making it likelier that they will not end up in the federal electronic records database, and that is even more of a problem with older records.

Gaps in the federal databases have often been noted in the context of background checks for gun purchasers, whose names are checked against those files, but far less attention has gone to the effect they have on other aspects of law enforcement, like sentencing and parole.

The F.B.I. said it could not comment on a specific case or the practices of individual agencies, but noted in a statement that participation “from our state and local partners is voluntary, not compulsory.”

Nevada officials noted that misdemeanor cases were sometimes expunged from the record years later, for defendants who stay out of trouble, and that records could be sealed by court order.

But the 1989 case appears, unsealed, in California’s database, where The Times was able to find it, and a spokeswoman for the Los Angeles County courts confirmed that the conviction was never expunged, remaining a part of Mr. Simpson’s record. Under California law, a no-contest plea is a conviction.

Mr. Simpson’s lawyer at the parole hearing, Malcolm P. LaVergne, said he was aware of the earlier case, but did not know why California would not have submitted it to the federal database.