The Oklahoma attorney general's office misrepresented the facts behind a key argument about the availability of certain execution drugs in its filings at the U.S. Supreme Court, BuzzFeed News has determined.

In the state's brief to the justices, Oklahoma Attorney General Scott Pruitt's office highlights a letter that the lawyers describe as having been sent to state officials. That letter is real — but it was sent to an entirely different state.

The false statement — which relates to discontinued availability of the drug pentobarbital — is clear from a review of previous court filings and comments from the lawyer for a pharmacy that the state claimed had previously supplied for its lethal injections.

Since Oklahoma lawyers argued before the Supreme Court on April 29 in defense of the constitutionality of its execution methods, BuzzFeed News has been looking into whether Oklahoma misled the court in its brief.

The state contends that they resorted to using the controversial execution drug midazolam because their other options dried up. At oral arguments, some of the more conservative judges posed questions about this issue.

In Oklahoma's brief, they state that the source of pentobarbital stopped supplying the drug to the state because the source faced "intense pressure" to stop.