A Texas prosecutor will appeal against a court ruling tossing out a five-year prison sentence for a woman who unintentionally tried to vote while ineligible in the 2016 election, an unexpected move that continues one of the most closely watched voting prosecutions in the US. Last month, the second court of appeals, which is based in Fort Worth, threw out the 2018 conviction of Crystal Mason, a Black woman who submitted a provisional ballot in 2016 that ultimately went uncounted. Mason was on supervised release for a federal felony at the time she voted and has said she had no idea she was ineligible. The panel said prosecutors had failed to prove Mason actually knew she was ineligible. But the Tarrant county district attorney, Phil Sorrells, a Republican, announced on Thursday he was appealing to the Texas court of criminal appeals, the highest criminal court in Texas. “The trial court’s guilty verdict should be affirmed. Voting is a cornerstone of our democracy. This office will protect the ballot box from fraudsters who think our laws don’t apply to them,” Sorrells said in a statement. “The second court of appeals’ publication of its opinion creates the very real risk that future sufficiency cases will likewise be wrongly analyzed and decided.” When election workers were unable to find Mason’s name on the voter rolls on election day in 2016, they offered her the chance to cast a provisional ballot. The key piece of evidence used to convict her was testimony from election workers saying they believed she had read an affidavit warning that someone cannot vote until they complete “any term of incarceration, parole, supervision, parole or probation”. Mason says she did not read the affidavit and that no one ever told her she could not vote. It is undisputed that she was never told she could not vote. “It is disappointing that the State has chosen to request further review of Ms Mason’s case, but we are confident that justice will ultimately prevail. The court of appeals’ decision was well reasoned and correct. It is time to give Ms Mason peace with her family,” Thomas Buser-Clancy, an attorney with the Texas chapter of the American Civil Liberties Union, said in an email. Mason has already had to serve an additional 10 months in federal prison while she appeals the state conviction. She remains free on an appeal bond and is living in Fort Worth. “I’m truly saddened at this moment that the state in this upcoming election is still sending a message,” Mason said in a text message. “I just don’t understand. My heart is very very heavy right now.”