Roy G. Saltman, the federal government’s leading expert on computerized voting whose overlooked warning about the vulnerability of punch-card ballots presaged the hanging chad fiasco in Florida and the disputed recount in the 2000 presidential election, died on April 21 in Rockville, MD. He was 90.

In a 132-page federal report published in 1988 and distributed to thousands of local voting officials across the country, Mr. Saltman, an analyst working for the National Institute of Standards and Technology, cautioned that the bits of cardboard that voters were supposed to punch out from their ballots, known as chads, might remain partly attached (hence, hanging), or pressed back into the card when the votes were counted. Either event would render the voter’s choice uncertain or, if the ballot appeared to be picking more than one candidate, invalid.

Mr. Saltman often said that there was no margin of error in voting. “An election is like the launch of a space rocket,” he often said. “It must work the first time.”