BIRMINGHAM, Ala. — An Uzbek man who pleaded guilty to plotting to assassinate President Barack Obama was never admitted to Columbia’s medical school, the university said Saturday, contrary to defense claims before he was sentenced to more than 15 years in prison.

The disparity could be a misunderstanding linked to language problems, a defense attorney said, but it also could raise questions about Ulugbek Kodirov’s credibility and the information he is giving to investigators of terror threats against the U.S. A federal judge sentenced Kodirov, 22, on Friday for plotting to kill Obama. U.S. District Judge Abdul K. Kallon agreed to prosecutors’ request for a shorter term because he has provided substantial assistance the government believes to be true.

The Columbia claim was important to the defense narrative because it explained how Kodirov wound up in Alabama, where he tried to purchase a weapon to kill Obama last year before his arrest. Defense lawyer Lance Bell told the judge that Kodirov was accepted to Columbia’s medical college, received a U.S. student visa and moved to New York but couldn’t enroll at the school because his English was too poor. But Columbia spokesman Doug Levy said Kodirov never was accepted to the College of Physicians and Surgeons.