The newest judge to win a seat on the criminal court bench at Tulane Avenue and South Broad Street was sworn in this week in a ceremony flush with promise, as state and federal judges, Sheriff Marlin Gusman, District Attorney Leon Cannizzaro and U.S. Attorneys past and present welcomed former prosecutor Byron C. Williams to the robe.

The oldest judge, meanwhile, was nowhere to be seen.

Conspicuously absent from the roster of Orleans Parish criminal court judges who took the stage for Williams’ investiture on Tuesday was Frank Marullo, the longest-serving jurist in Louisiana,

Marullo can be excused, having turned 75 on Wednesday — an inauspicious milestone that leaves him girding for an inevitable legal challenge to his right to serve another six years.

The fight could start soon, with a widely expected complaint — from whom is not clear — to the state Judiciary Commission. Ultimately the decision over Marullo’s status will fall to the Louisiana Supreme Court, which has the sole power to remove a sitting state judge.

Marullo’s Dec. 31 birthday could prove hard to overcome.

While the 4th Circuit Court of Appeal ruled last fall that there was nothing to stop him from running for re-election — a decision the state’s high court refused to upend — the appeals court also made clear that the rules for actually taking the bench are another matter entirely.

The current state Constitution sets a 70-year mandatory retirement age for judges — a cap that statewide voters refused to abandon this year, even as more than half of New Orleans voters backed Marullo for a new term and also supported the failed amendment to abolish the age limit.

Marullo, though, claims he falls under the old, 1921 Constitution, which had settled on a hard, 75-year age cap by the time then-Gov. Edwin Edwards appointed him 40 years ago.

Marullo sees legal wiggle room in the “soft” cap under the existing constitution, which allows judges to serve out their terms if they hit the mandatory retirement age while in office.

But that best-of-both-worlds legal argument may be trumped by the fact that Marullo came into the world two minutes before the New Year’s Eve ball dropped in 1939.

Critics claim that, at age 75, neither constitution helps him.

Attorney Jim Boren, who helped defend Marullo’s right to stay on the ballot last fall, said this week that he wasn’t yet ready to reveal the legal strategy for keeping Marullo on the bench into his 80s.

But in a possible preview last fall, Boren noted that while state law declares that a judge’s term ends on Dec. 31, it doesn’t explicitly state when it begins. The suggestion: Sitting judges can, and have, started their new terms before the New Year.

As it happens, Marullo took his latest oath of office quietly in his chambers on Dec. 19, with Criminal District Judge Franz Zibilich doing the honors.

If all else fails, Marullo has hinted at a broader age-discrimination argument.

“What does age have to do with your qualifications, if you can function? People might dislike the way I function, but I function pretty good,” Marullo said after taking the November primary over two much younger opponents, Graham Bosworth and Marie Williams.

“In America, age should not play a part in any of this.”

At age 60, Williams has no such worries.

The former state and federal prosecutor was handed a bible and fitted with a black robe in a prolonged ceremony at the Ellis Marsalis Center for Music, in Musicians’ Village. Jazz clarinetist Dr. Michael White performed a stirring solo rendition of “Over the Rainbow” before Williams’ two-time boss, former Orleans Parish DA and U.S. Attorney Eddie Jordan, waxed on about what he described as an improbable election day win by Williams over Municipal Court Judge Paul Sens.

U.S. Attorney Kenneth Polite Jr., state Rep. Walt Leger and City Councilwoman Susan Guidry were among several local elected officials in attendance. U.S. District Judge Brian Jackson, chief judge of the Middle District of Louisiana, administered the oath.

Williams, who beat Sens with 67 percent of the vote, said his first task will be to get a handle on one of the court’s most bloated, dog-eared dockets, left behind by Judge Julian Parker, who declined to run again after 17 years on the Section G bench.

“The most obvious thing is to find the oldest cases and start moving them off the docket,” said Williams, a graduate and former football player for St. Augustine High School. “I know there are some old cases.”

According to the most recent Metropolitan Crime Commission report on the judges, 40 percent of the cases in Section G have lingered for more than a year — a figure that has likely grown considerably since Parker stepped off the bench in August, leaving his caseload to a rotation of fill-in judges.

No other criminal court judge in Orleans Parish faced an election-day challenge this year.

Follow John Simerman on Twitter, @johnsimerman