“We do not pretend to understand why the defendant chose to go down such a treacherous path,” Circuit Judge Bruce M. Selya wrote of Tarek Mehanna, now 31.

Calling terrorism “the modern-day equivalent of the bubonic plague,” a federal appeals court in Boston upheld Wednesday the conviction and 17½-year prison term handed down to a Sudbury man on charges that he helped Al Qaeda, plotted to kill Americans, and lied to the FBI.

Tarek Mehanna of Sudbury was convicted in 2012 of conspiring to kill American soldiers and support and Al Qaeda.

“Nevertheless, the jury found that he knowingly and intentionally made that choice,” a finding backed by the “clear weight of the evidence,” Selya wrote for a three-judge panel of the US Court of Appeals for the First Circuit.


Mehanna’s lawyers could not be reached for comment. A call to a number listed for his family was not returned Wednesday.

A federal jury in Boston convicted Mehanna in December 2011 on charges of conspiring to provide material support to terrorists, conspiring to kill in a foreign country, and of lying to authorities in a terrorism investigation.

Prosecutors said during Mehanna’s trial that he traveled with an associate to Yemen in 2004 to join a terrorist training camp and ultimately attack American soldiers in Iraq, but the plan failed.

When Mehanna returned home, prosecutors said, he began translating Arab-

language materials into English and posting them online to promote Al Qaeda’s ideology and inspire others to violent jihad.

Mehanna’s lawyers argued that he traveled to Yemen to pursue religious studies, but the appeals court wrote Wednesday that the evidence pointed to a more sinister aim.

Coconspirator testimony indicated, Selya wrote, that the purpose of the trip was “to basically fight in a war” and that Mehanna felt Muslims had an obligation to fight US forces in Iraq.

Regarding his translations, Mehanna’s lawyers and free speech advocates argued that his actions were protected under the First Amendment.


“The fundamental problem with the [appellate] ruling is that it allows the government to prosecute unpopular political speech,” said Alex Abdo, staff attorney at the ACLU’s National Security Project.

Selya wrote that even if prosecutors failed to prove the translations amounted to material support for Al Qaeda, the conviction on terrorism-related charges is “independently supported by the mass of evidence surrounding the Yemen trip.”

Defense lawyers had also argued that prosecutors had improperly sensationalized the trial by repeatedly showing images of Osama bin Laden and suicide bombings to prejudice jurors.

Selya wrote that the images, which Mehanna “absorbed and endorsed,” related to his “motive and intent” in traveling to Yemen.

Selya added that terrorism evidence, by its nature, is often emotionally charged and could offend jurors.

“Terrorism trials are not to be confused with high tea at Buckingham Palace,” he wrote.

The Tarek Mehanna Support Committee, a grass-roots organization, blasted Wednesday’s ruling.

“The appeals court decision is outrageous, but we will continue to stand by Dr. Mehanna,” the committee said.

“The court’s likening of terrorism to ‘the modern-day equivalent of the bubonic plague’ is an example of the kind of sensational language that ensured a biased trial against Dr. Mehanna in the first place.”

But US Attorney Carmen M. Ortiz, whose staff prosecuted Mehanna, hailed the ruling in a statement.

“We are gratified that the Court of Appeals carefully reviewed the case, found the evidence of the defendant’s guilt was more than sufficient to convict the defendant, and held that it was ‘confident’ that, in the court’s words, [Mehanna] ‘was fairly tried, justly convicted and lawfully sentenced,’ ” Ortiz said.


Milton J. Valencia of the Globe staff contributed to this report. Travis Andersen can be reached at travis.andersen@globe.com.