What would a new Tsarnaev trial look like, five years later?

For three long months in 2015, victims and their families were forced to endure the trial of Boston Marathon bomber Dzhokhar Tsarnaev, an emotionally devastating proceeding that concluded with an unremorseful Tsarnaev being sentenced to death for his role in a plot that left three dead and wounded hundreds.

Now, they might have to do it all over again.

From the moment last week that a federal appeals court vacated Tsarnaev’s death penalty sentence, citing issues with jury selection in the case, the prospect of enduring a second trial has hung over a city that had hoped to put this brutal episode behind it.

“Unfortunately, I think if there’s a retrial on life vs. death, it’s going to be very similar to what we already experienced,” said Daniel Medwed, a professor of law and criminal justice at Northeastern University. “And it would reopen a lot of wounds not only for victims, but for many Bostonians.”

While it’s possible that federal prosecutors could simply accept the panel’s findings and elect to go no further — Tsarnaev’s sentences of life in prison without the possibility of parole remain intact under the ruling — legal experts and former federal prosecutors said this week that it is highly unlikely given the current political climate.

As President Trump has increasingly clung to a tough-on-crime ethos as a centerpiece of his reelection bid, many expect the president to use the Tsarnaev case — a horrific episode representing a dark chapter in the city’s history — as an election-year cause celebre.

Even as the death penalty has recently fallen out of favor with Americans, the Trump administration has made no secret of its support for capital punishment. After nearly two decades without a federal execution, Attorney General William Barr has ordered three executions to be carried out in the last month alone. And already, Trump has made it clear what he expects from the Tsarnaev case moving forward.

“Death penalty!” he said on Twitter over the weekend, in response to news of the appellate ruling. “He killed and badly wounded many. Justice!”

“This administration clearly has very much an agenda around capital punishment,” said Carol Steiker, a law professor at Harvard Law School. “They have made capital punishment an issue in an election year because they’re playing by the 1960s, ’70s, ’80s playbook — the tough-on-crime playbook that brought Richard Nixon into office.”

“It’s just hard not to see that as political,” she added. “And if that’s right, you would expect them to really pound on the table with this one, because of all the emotion that’s raised by the heinousness of this crime.”

If the Justice Department does decide to again pursue the death penalty against Tsarnaev, as many predict, it would have three potential paths.

First, prosecutors could seek a review of the First Circuit’s ruling in a process known as “en banc,” in which last week’s ruling would be reexamined by the full panel of the First Circuit Appeals Court, rather than just a three-judge panel. Prosecutors could also take the ruling directly to the Supreme Court, which, if it decided to hear the case, could vote to reinstate the death sentence.

But while both of those options are relatively low-risk, federal prosecutors might also choose to go straight to a new trial, a move that could potentially avoid months, if not years, of legal wrangling.

A new trial, say those familiar with the federal court system, would look strikingly similar to the first, right down to the inevitable media spectacle.

A new jury would need to be selected. The question of venue would again be debated. And though last week’s ruling only involved the sentencing phase of the trial — Tsarnaev’s guilt wasn’t called into question — it remains possible that a second trial could take even longer than the first, as jurors would have to be brought up to speed and new information would likely be presented.

“The fact that it’s a resentencing doesn’t mean that the government doesn’t have to present its case about what actually happened,” said Robert Dunham, executive director of the Death Penalty Information Center, a national nonprofit organization. “The jury won’t be deciding guilt or innocence, but they will need to know what the facts are.”

The scenario is not without precedent.

After a Massachusetts jury sentenced Gary Lee Sampson to death in 2003 for three murders carried out across two states, a judge later overturned the verdict when it came to light that one of the jurors in the case had lied about her background.

During a retrial in 2017, a second jury condemned Sampson to death.

But there are risks, too.

Included in last week’s ruling was the panel’s determination that certain information should have been disclosed to the defense prior to the original trial, including the alleged violent actions of Tsarnaev’s older brother, Tamerlan, which the defense would likely use as a mitigating factor to show that Tsarnaev was influenced by his brother. That could hinder the prosecution’s case.

What’s more, a new trial would come at a steep cost, both in the time and money required to regather witnesses and legal teams in the middle of a global pandemic — all in pursuit of a death sentence that, even if it were handed down again, might never actually be carried out.

“It’s almost symbolic,” said Nancy Gertner, a former federal district court judge who now teaches criminal law at Harvard Law School. Even if a jury again rendered a death sentence, “it could take years and years and years for this verdict to become final, and who knows what the politics in those days would be?”

Indeed, while federal executions have recently picked up under the Trump administration, they remained exceedingly rare in the preceding decades; between the late 1980s and 2019, only three of the more than 500 defendants facing federal capital punishment were actually executed. Public support for the death penalty has waned, too, with a 2019 Gallup poll showing that, for the first time, the majority of Americans supported life imprisonment over the death penalty.

There’s always the possibility, meanwhile, that a new presidential administration could elect to shelve any effort to retry the case.

If a new trial does come to pass, it’s unlikely it would be held any time soon due to COVID-related court delays.

As of now, all federal jury trials scheduled in the District Court of Massachusetts through Sept. 8 have been continued, with the possibility of additional delays. And even as federal trial courts reopen, they’ll do so under restrictions and safety protocols that could “make it impossible to try a death penalty case,” said former federal prosecutor George Vien.

In a city still working to recover from the bombing and its aftermath, meanwhile, there is also the issue of emotional toll.

And despite the political implications of the case, the potential for added trauma, some say, should be strongly considered in any decision on whether to push forward.

“There are reasons that the government may want to do it,” said Dunham, of the Death Penalty Information Center. “But when the government makes that choice, it has long-term psychological consequences for everyone who was involved.

“So the question becomes: How much is that cost worth?”

Dugan Arnett can be reached at dugan.arnett@globe.com.