US prosecutors drop charges against scientist detained over frog embryos

US federal prosecutors have dismissed all criminal charges against Russian scientist Kseniia Petrova, 31, after she spent four months in immigration detention following her arrival in Boston with frog embryos intended for cancer research at Harvard Medical School, prosecutors said.

Petrova was taken into custody in March 2025 when she returned from a vacation in France, where she visited a lab that cuts extremely thin sections of frog embryos, according to court records. Customs officials questioned her about the samples at Logan International Airport and later charged her with smuggling, concealing facts and making false statements to government officers.

The case was highlighted as part of a series of high‑profile immigration‑related arrests of academics after Donald Trump returned to the White House promising a crackdown, officials noted. Petrova had fled Russia after being arrested for protesting the invasion of Ukraine, and colleagues at Harvard described her research talent as “spectacular”, they said.

On Wednesday, US District Judge Leo Sorokin granted the prosecution’s request to dismiss the case without a hearing, court documents show. The dismissal followed an earlier finding that a customs officer had improperly cancelled Petrova’s visa, prompting her fear of deportation to Russia where she could face imprisonment, authorities explained.

US Attorney Leah Foley filed a motion on Tuesday night seeking to drop the case, stating that “at this stage, the resource costs of continuing this prosecution outweigh the public interest in its resolution” and describing the defendant’s claims of vindictive prosecution as “meritless”, the filing read.

Petrova’s lawyer Daniel Marx criticised the prosecution, saying “The DOJ never should have brought this highly unusual ‘smuggling’ prosecution against Kseniia Petrova, a talented scientist at Harvard” and adding that the frog embryos were inert, non‑living and posed no danger, he said in a statement.

The Department of Homeland Security continued to defend the arrest, maintaining that Petrova had lied to federal officers about the frog embryos, and she joins a number of non‑citizen academics who have faced arrest or deportation threats under the Trump administration, officials said.