Rarely, if ever, has someone twice elected to New Orleans’ highest office seemingly had so few friends.

As judgment day approaches for Ray Nagin, plenty of interested observers — ranging from the prosecutors who convicted him to a host of average citizens — are calling on U.S. District Judge Ginger Berrigan to show him no mercy when she sentences him Wednesday.

No mercy, in this case, likely means a term of roughly 20 years in a federal penitentiary, a punishment that Nagin’s lawyer has said would mean a “virtual life sentence” for the former mayor, now 58.

Nagin’s many detractors cite a multitude of reasons why Berrigan should drop the hammer. They say he failed to lead his city in its darkest hour. They cite his divisive “Chocolate City” speech. And they point to his failure to own up to any real wrongdoing, save perhaps cozying up to some shifty characters — most memorably in a breezy and sometimes infuriating two-day turn on the witness stand during his February trial.

The former mayor’s supporters, a shockingly small contingent, given that more than 76,000 New Orleanians pulled the lever for Nagin in his first election, point to his Christian values, his love for his family and his lack of a prior criminal record. About four dozen people, including a number of Nagin’s relatives, have written the court, almost all of them asking for leniency.

But while Berrigan is certainly aware of the strong feelings Nagin arouses — particularly, it seems, among those who despise him — most of it qualifies as mere noise in the background. The punishment she metes out will be based on a strict set of guidelines, a matrix that contains some wiggle room but is essentially an elaborate math problem.

A key 2005 U.S. Supreme Court decision, U.S. v. Booker, made federal sentencing guidelines advisory rather than mandatory, meaning that judges have some flexibility to go outside those ranges. But that flexibility is limited in practice.

Once Berrigan calculates the sentencing range that she believes the law calls for on each crime for which Nagin was convicted, she’ll likely have to hew pretty closely to it, or risk being overturned, experts say.

As with all federal criminal cases, the framework for Nagin’s sentencing is laid out in a document prepared in advance by federal probation officers. That report, which is sealed, computes what that office sees as the “offense level” for Nagin’s crimes, with points assigned according to specific aspects of the case. The offense level translates into a range of appropriate sentences, as determined by the U.S. Sentencing Commission and published in a chart.

Berrigan, generally considered the Eastern District of Louisiana’s most liberal jurist, will come up with her own analysis.

Adding it up

Under the rules, Nagin starts with a base “offense level” of 20 because he was an elected official who took multiple bribes but otherwise has no criminal history — facts that, with the jury verdict, are now undisputed.

The other major factors that will add points to his offense level include the financial “loss” the court assigns to his actions, the court’s judgment as to whether he was an “organizer or leader” in “criminal activity” that involved at least five people, and whether Nagin is found to have obstructed justice by lying to investigators and to the court.

There is some gray area in all of these questions. For instance, the monetary loss can be calculated to include not only bribes paid and received, but also the proceeds of any contracts that resulted from bribes.

At a minimum, however, Berrigan will almost certainly find that the loss was greater than $200,000, as the jury convicted Nagin of taking more than that amount in bribes. That would bring his offense level to 32, but it could go significantly higher depending on whether Berrigan decides to include the profits of some or all of the contracts Nagin signed.

Were the judge to use the amount of “ill-gotten gains” she has ordered Nagin to forfeit — $501,500, which includes the money his granite company took in from a deal with Home Depot — the offense level would jump to 34. If she includes the profits from contracts won by firms owned by those who bribed Nagin, the number could go higher.

Imperfect measures

Experts say the question of financial loss is among the thorniest in calculating guidelines. The amount of bribes paid is an imperfect measure, for contracts awarded on the basis of bribes are presumed to be inflated to cover the cost of the payoffs. At the same time, the contractor usually completes the work outlined in the contract, making it unfair to count the entire value of the contract as a loss. In Nagin’s trial, the government did not present evidence to show that those who bribed Nagin failed to perform.

“I think looking at the big numbers on the contracts distorts the criminality,” said Herbert Larson, a veteran defense lawyer. “What I would be arguing is: Did the city receive benefits from that contract, and what was the value of those benefits? You subtract that value out, and presumably the rest is fraud.”

Other questions are similarly nuanced. If Berrigan finds Nagin obstructed justice by lying to investigators and to the jury, as prosecutors say he did on more than 25 occasions, the offense level would jump another two points. And if she finds he took a leadership role in a scheme involving five or more people, that would add as many as four more points.

Though it’s clear that Nagin’s criminal conduct involved more than five people, experts say there may be wiggle room in that question, too. Larson said he’d argue that the case is more properly viewed as a series of conspiracies involving Nagin and one or two others — a so-called “hub and spoke” conspiracy — rather than a single scheme involving the whole group.

Depending on how the judge rules on those questions, Nagin’s final offense level could be as low as 32, or as high as 40 or more. Based on those numbers, the guidelines would call for a sentence ranging from 10 years at the low end to as much as 30 years or even life.

A filing by Nagin’s lawyer, Robert Jenkins, suggests that probation officers came up with an offense level of 38, which translates to a range of 20 to 24 years.

Request for leniency

Jenkins asked Berrigan to consider a downward departure from that figure based on Nagin’s lack of a criminal history and an argument that the crimes of which he was convicted constituted “aberrant” behavior for an otherwise upstanding citizen.

But prosecutor Matt Coman argued in an opposing motion that the guidelines already take into account the mayor’s unblemished past, which they do. Meanwhile, Coman said it was laughable to consider Nagin’s criminal conduct as an aberration, considering that he was convicted of multiple bribery and fraud schemes that unfolded over a period of years.

Pat Fanning, a veteran federal defense lawyer and former prosecutor, agreed with Coman’s assessment, saying that judges generally consider criminal behavior to be aberrant only when it involves a single act. “I don’t think he has an argument there at all,” Fanning said.

While Berrigan may thus brush aside Jenkins’ request, she may still quibble with other aspects of the presentence report. That’s not unusual in criminal cases, especially given the gray areas inherent in the guidelines. In fact, it happened in the case of another defendant represented by Jenkins — former Jefferson Parish President Aaron Broussard, for whom the probation office recommended a sentencing range of 78 to 97 months.

The judge in that case said the guidelines had been misapplied. He came up with a range of 46 to 57 months and gave Broussard the most lenient sentence within that range, calling his criminal conduct “sophomoric.”

Appellate courts tend to defer to district court judges in deciding how to apply the guidelines in gray areas, such as whether the defendant took a leadership role or perjured himself, said Robert Weisberg, a law professor at Stanford University who is an expert on sentencing guidelines. But the higher courts will not hesitate to order a new sentencing hearing if they believe the lower court judge factually misinterpreted the guidelines, he said.

That happened recently in the case of former City Councilwoman Renee Gill Pratt, whom U.S. District Judge Ivan Lemelle initially sentenced to seven years. The 5th U.S. Circuit Court of Appeals found that Lemelle had miscalculated the numbers and ordered a new hearing. He recently resentenced Gill Pratt to four years.

Will Nagin speak?

Apart from applying her own analysis of the guidelines, Berrigan also has some ability to go outside the recommended range, experts said. She could grant a “downward variance” on some basis she deems appropriate, provided that she explains it and the variance is not too great. Federal law spells out a number of factors a judge may consider, from the need to protect the public from further crimes to the deterrent effect of the sentence.

Fanning said a client of his, Bay Ingram, who was convicted of overbilling BP for helicopter rides after the 2010 Gulf oil spill, received a sentence of 18 months instead of the 24 to 30 months outlined in the guidelines. In granting a bit of leniency, U.S. District Judge Sarah Vance cited Ingram’s record of charity and the huge number of letters she received in his support.

Most experts said the appellate courts are apt to grant judges that level of discretion — that is, they won’t overturn a sentence that is not far outside the guidelines.

“It’s an incredibly subtle balancing act,” Weisberg said. “It’s like, ‘We’re not saying you have to stay within the guidelines, but don’t go too far from them.’ ”

One factor that could play a role is whether Nagin speaks at the hearing and what he chooses to say.

When defendants plead guilty, they typically give an “allocution” — a speech to the court apologizing for their behavior that can sometimes sway judges.

But Nagin did not plead guilty, and although he was convicted by a jury, he has never admitted to any wrongdoing, even creating a website to raise money for a legal defense fund in which he steadfastly maintains his innocence.

“In my experience, the kind of speech a defendant gives at sentencing can matter a lot to what judges decide to do, especially within the (sentencing) range,” said Tania Tetlow, a former federal prosecutor and now a professor at Tulane Law School. “I’ve seen judges cross out what they had written down and change it based on what the defendant does. But if he’s not prepared to fall on the sword and beg for mercy, he may say very little. And he seems pretty determined to maintain his innocence.”

Follow Gordon Russell on Twitter, @gordonrussell1.