An appeals court has ruled that a state law that gives a $250 fee to the Tennessee Bureau of Investigation for each DUI conviction obtained using a blood or breath test is unconstitutional.

Tuesday's ruling by the Court of Criminal Appeals in Knoxville says the system violates due process and calls into question the trustworthiness of TBI forensic scientists' test results. It says the system creates a monetary interest for forensic scientists through continued employment, salaries, equipment and training.

State lawmakers passed a TBI-backed proposal in 2010 to raise the fee from $100 to $250.

The ruling says the fees total about $3 million annually.

It's unclear if prosecutors will appeal to the state Supreme Court.

The case involves more than 20 defendants who provided blood or breath samples.