US prosecutors have dropped all criminal charges against Kseniia Petrova, a Russian scientist at Harvard Medical School who was detained after arriving at a Boston airport with frog embryos intended for medical research.
Petrova, 31, was arrested at Boston Logan International Airport in February 2025 after returning from a trip to France, where she had obtained biological samples for research at Harvard.
Customs officials found the undeclared frog embryo samples in her luggage, leading to charges of smuggling, concealing material facts and making false statements to federal authorities.
She spent nearly four months in immigration detention before being released on bail in June 2025. Petrova pleaded not guilty to the charges and maintained that she had been asked by her research supervisor to transport the samples for experiments.
The case took a new turn after a federal judge ruled in April 2026 that immigration authorities had unlawfully cancelled her visa over the incident. Her lawyers subsequently argued that the criminal prosecution was selective and vindictive.
Federal prosecutors sought to dismiss the charges, saying the resources required to continue the case outweighed the public interest in pursuing it. They maintained, however, that Petrova’s claims of selective prosecution were without merit.
US District Judge Leo Sorokin approved the dismissal on November 4, 2026, ending the criminal proceedings against the researcher.
Petrova’s lawyer welcomed the decision, arguing that the prosecution should never have been brought against her, and said the samples were non-living and posed no danger.
The case attracted attention over the treatment of foreign researchers and the immigration consequences of carrying biological research materials across international borders.
