(CNN) Ledell Lee was likely innocent when Arkansas executed him in April 2017, says a lawsuit that calls on authorities to release evidence that could prove it.

Lee was the first person executed in Arkansas in more than a decade. He also was the first in a string of executions the state planned to carry out in days to use lethal-injection drugs before they expired.

Lee maintained his innocence until the end, says the lawsuit, which asks the court to order the city of Jacksonville and its police department to release DNA samples and fingerprints to be tested and run through national databases.

"My family has been unable to rest for the last two and a half years, knowing that my brother was murdered by the state of Arkansas for a crime we believe he did not commit," Patricia Young, the plaintiff and Lee's sister, said in a statement from the ACLU.

What happened to the murder victim, Debra Reese, was "horrible," Young said. "But I was with Ledell the day this murder happened, and I do not see how he could have done this."

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