To the surprise of many in the standing-room-only courtroom in City Hall, Knorr agreed with the justice.
The federal government's Homeland Security laws forced PennDot to require some additional proof before providing citizens with identification cards, Knorr explained, so the agency could not comply with that provision of the law.
That was part of the reason the state came up with yet another form of photo ID, never mentioned in the voter-ID law, that became available to the public in late August, Knorr said.
The new ID, also issued by PennDot but referred to within the transportation department as the "Department of State ID," requires registered voters to provide two numbers that every citizen should have - a date of birth and a Social Security number - along with proof of residency.
The significance of Saylor's questioning and Knorr's answers was left unclear. The justice did not indicate that it would sway his vote one way or the other on whether the voter-ID law should remain in force for the November election.
But it followed a presentation by opponents of the law in which David Gersch, a lawyer with the Washington law firm Arnold & Porter, told the court the main problem with the law was its failure to ensure that all voters could get the ID now required to vote at the polls in November.
There was nothing inherently unconstitutional about the legislature's requiring voters to prove their identities with photo-ID cards, Gersch said, but "at some point, for this to work, the state has to make sure that every person will be able to get the identification they need."
With the Nov. 6 election now less than eight weeks away, Gersch said, "there is too little time, too many people, and nothing in the statute that guarantees people will be able to get the ID they need."
Knorr and Alfred W. Putnam Jr., representing Gov. Corbett and Secretary of State Carol Aichele, urged the court to uphold the finding of Commonwealth Court Judge Robert E. Simpson Jr. that the ID law was an appropriate exercise of the legislature's authority to set the rules for state elections.
"What's the rush?" asked two justices, Debra McCloskey Todd and Seamus McCaffery, grilling the state's attorneys on why the legislature was determined to implement the law in November, with a presidential race on the line and Pennsylvania regarded in some quarters as a swing state.
The legislature approved the bill along partisan lines - Republicans for, Democrats against - before Gov. Corbett signed the measure.
Republican leaders say the law will deter voter fraud, though there have been no documented cases in recent state history of any voter trying to impersonate another.
McCaffery made reference to comments by House Majority Leader Mike Turzai (R., Allegheny), who told a roomful of Republicans in June that the law would help Mitt Romney win Pennsylvania.
"Could there be politics, maybe?" McCaffery asked, prompting a spurt of laughter among more than 100 spectators.
"We, as a court, do accord great deference to the legislature," Todd said. "But when done so close to a federal election . . . it seems to me that degree of deference may be somewhat dissipated."
The justices concluded the hearing after a mere 85 minutes and now begin their deliberation.
Chief Justice Ronald D. Castille, regarded as a possible swing vote among the six justices, asked few questions and gave no indication of how quickly the court might reach a decision.
The court is split 3-3 between justices elected as Democrats and those elected as Republicans. If they were to split 3-3 on the voter-ID case, Simpson's decision would stand.
Before the hearing began, leaders of the NAACP, the Philadelphia Neighborhood Network, and MoveOn.org staged an hour-long rally against the voter-ID law on Thomas Paine Plaza across from City Hall.
The NAACP's national president, Benjamin Todd Jealous, denounced the law as a bid by Republicans to steal the presidential election.
Contact Bob Warner at 215-854-5885 or email@example.com.
Inquirer staff writers Angela Couloumbis and Peter Mucha contributed to this article.