(CNN) A Texas mother sentenced to five years in prison for voting illegally in the 2016 election appealed her conviction Tuesday, saying she did not know her status as a felon on release made her ineligible to cast a ballot.
Crystal Mason, an African-American mother of three, was on supervised release after serving time for tax fraud when she filled out a provisional ballot. She has said she did not know that as a convicted felon in Texas, she could not vote until the supervised release was complete.
Tuesday's half-hour hearing before a three-judge panel in Fort Worth focused largely on whether the provisional ballot that Mason cast actually constitutes a vote. A court representative told CNN there is no date set for a decision.
Mason, 44, and her supporters see her appeal as part of a broader fight to preserve voters' rights amid a crackdown on what some election officials allege is rampant fraud at the ballot box.
Mason "stepped forward to challenge the injustice that was done to her by this state's politicians, who were willing to deprive her of her liberty for five years for their own insidious political agenda," Beth Stevens, an attorney with the Texas Civl Rights Project, told reporters after the hearing. "No one should be incarcerated for, at worst, under the state's theory, making a mistake when they go cast a vote."
Voting rights activists compare Mason's case to other voter fraud convictions, such as Terri Lynn Rote, an Iowa woman who tried to cast two votes for President Trump, and Russ Casey, a Texas justice of the peace who admitted to turning in fake signatures in order to get on a primary ballot. Those defendants, who are white, received sentences of two and five years' probation.
There are few cases of ineligible voters casting ballots and a smaller number still that lead to prosecutions, said Wendy Weiser, who directs the Democracy Program at the Brennan Center for Justice at New York University's School of Law.
In cases of ineligible voting, prosecutors and judges usually find "no basis" to believe the individual had any criminal intent, Weiser said.
That's what Mason says -- that she did not know she was not allowed to vote and would never have run the risk of leaving her family again for prison in order to cast a ballot.
"There's no way that I would have attempted to vote, to leave my children, to lose my job, to go through what I'm going through right now," Mason told CNN in a May interview at her Dallas church.
In court Tuesday, Tarrant County assistant district attorney Helena Faulkner said, "She knew she was ineligible to vote. She wasn't mistaken."
Sam Jordan, a spokeswoman for the Tarrant County Criminal District Attorney's Office, said in a statement to CNN it should have been clear to Mason she was ineligible to vote. She said a letter was sent to her home after her tax fraud conviction -- one Mason says she didn't receive, since she was incarcerated -- and a written warning was on the side of the provisional ballot she filled out in 2016.
Mason didn't read the warning, she said, because she was focused on filling out personal information on the other side of the form.
In her appeal, Mason's defense disputed whether it's correct to say she even voted at all, since her provisional ballot was rejected and never tallied. The county elections administration sent Mason a letter explaining her vote was rejected because she was not a registered voter, according to the American Civil Liberties Union, which is part of her legal team.
Mason's lawyers have also argued that it is unclear whether Mason was truly ineligible to vote, saying her status was ambiguous while under federal supervised release.
Andre Segura, legal director of the ACLU of Texas, said Mason's case is the first one the advocacy group knows of in Texas in which someone is prosecuted for casting just a provisional ballot.
"This is an example of an individual (who's) following procedures that are put in place, safeguards that already exist," said Sophia Lakin, an attorney with the ACLU's Voting Rights Project who attended the Tuesday hearing. A sentence of five years in prison, Lakin said, "really is outsize and outrageous" for making "what normally would be seen as an a understandable mistake."