Scientist who brought frog embryos to Boston for cancer research is cleared of smuggling charges

U.S. prosecutors have dropped all criminal charges against a Russian scientist who was tossed into an immigration jail last year after she landed at a Boston airport with frog embryos intended for her cancer research at Harvard Medical School.

Kseniia Petrova, 31, spent four months in detention following her arrest in early 2025 as she returned from a vacation in France, where she had stopped at a lab specializing in splicing superfine sections of frog embryos and obtained a package of samples for research.

She was questioned about the samples while passing through a customs checkpoint at Logan International Airport, then later charged with smuggling.

A federal judge on Wednesday granted a request by prosecutors to dismiss those charges as well as counts alleging that she'd concealed facts and made false statements to government officials.

Petrova told The Associated Press in an interview that she did not realize the items needed to be declared and was not trying to sneak anything into the country.

The case began to fall apart in April, after a federal judge ruled a customs officer improperly canceled Petrova's visa over the incident. Petrova had feared being deported to Russia and imprisoned there.

Her lawyers had also argued that the criminal prosecution was vindictive, saying the government only filed criminal charges after it looked like she would win her immigration case. They also argued that it was rare for anyone to be charged criminally for what Petrova did.

On Tuesday night, U.S. Attorney Leah Foley filed a motion to dismiss the charges “based on developments in this case and an assessment of the office’s priorities and resources.”

“At this stage, the resource costs of continuing this prosecution outweigh the public interest in its resolution,” she wrote, adding that the “defendant’s claims of vindictive and selective prosecution are meritless.”

U.S. District Judge Leo Sorokin, who was nominated by former President Barack Obama, dismissed the charges Wednesday without a hearing.

“The DOJ never should have brought this highly unusual “smuggling” prosecution against Kseniia Petrova, a talented scientist at Harvard,” one of Petrova's attorneys, Daniel Marx, said in a statement. “Ms. Petrova only sought to advance medical research into aging that could benefit everyone, and her handling of scientific samples — inert, non-living, non-toxic, frog embryos — never posed any danger to anyone.”

Earlier this year, the Department of Homeland Security defended Petrova's detention, saying she had lied to federal officers about the frog embryos.

In a court filing asking the judge to dismiss the case, Foley cited an April court ruling that would have allowed Petrova's lawyers to get broad access to government documents as part of her defense that she was being prosecuted selectively.

“The government must supply the defendant with information pertaining to any number of passenger encounters involving undeclared items that could be considered comparable, without regard for the manner in which those items were carried, the presence or absence of planning, or the strength of the evidence of a passenger’s fraudulent intent,” Foley wrote.