FORT WORTH, Texas -- At least two dozen drug cases in Tarrant County Criminal Court are under review because they were prosecuted as felonies instead of misdemeanors.

The cases involve the prescription substances Adderall and Vyvanse, according to a letter obtained by News 8 that was recently distributed to area defense attorneys.

The letter from Tarrant County District Attorney Sharen Wilson says that during the past legislative session, Senate Bill 172 effectively changed how the two drugs were classified, meaning now they can only be pursued as "...class B misdemeanors under 'miscellaneous substances,' rather than felonies."

The changes went into effect Sept. 1, 2015 -- more than a year ago.

But defense attorneys like Alex Kim were only notified by the DA's office six weeks ago that there had been cases prosecuted incorrectly.

Alex Kim

"My first concern was if I had any clients that were impacted," Kim said. "With a felony conviction, we're talking about going to prison, no longer being able to purchase a firearm [...] even voting."

Kim determined he didn't have any clients directly impacted. That isn't the case for everyone.

The district attorney's office says 11 cases were pending, and another 13 had already been disposed of when they became aware of the problem.

In a statement, DA Sharen Wilson said "The Legislature made the change in the law to account for K-2, but it had the unintended result of causing this change, as well, necessitating Brady disclosure... [each] defendant has been notified."

The office's Conviction Integrity Unit, which Wilson actually started, is helping resolve the issue.

She said the law change didn't have a "wide-scale effect in Tarrant County." Others aren't so sure.

Bryan Wilson says it can take time to determine how many cases are actually linked to a mistake like this, and that even when they are cleared defendants may face ongoing issues.

Bryan Wilson

"Even having just the felony arrest or charge can be a problem," the defense attorney said. "If you don't have that thing completely dismissed and either sealed or expunged, where they destroy the records, it's getting to haunt you."

Kim and Wilson both say they applaud the DA's decision to be forthcoming about the mistake.

Other Texas counties may be facing a similar issue, although it isn't clear just how many have sent out disclosure letters.

"This totally went under the radar for everyone in the state of Texas," Kim said.

Tarrant County DA's letter to criminal defense attorneys by wfaachannel8 on Scribd