UPDATE: A court ruling may affect DUI cases in Tennessee.

The law in question states that for every DUI conviction using a blood or breath test, the TBI receives $250. 

The ruling stems from a challenge by Chattanooga attorney, Jerry Summers and his client, Rosemary Decosimo. Decosimo was arrested for DUI in 2012 and pleaded guilty last year, but Summers argued his client's blood test should be thrown out because the fee system violated her right to fair trial and gave the TBI financial motivation to get convictions. 

"Follow the money and when you equate justice and money I believe that justice always loses," said Summers. 

Throughout court proceedings in Chattanooga, Summers believes the TBI worked on an incentive.

"It became a very lucrative fine that they were able to develop money to use for anything they really thought was consistent with enforcing the laws of the state of Tennessee and that still in our opinion infringement upon due process of law," said Summers. 

The fee was first introduced in 2005 and was originally $100. Five years later, it was raised to $250 based on a proposal from the TBI. According to the appeals court, the TBI collects more than $3 million a year from the alcohol tests, which is "reserved exclusively for the use of the TBI."

"The courts always look for any other reason not to determine the statute unconstitutional that's the last thing they look at. In our case they didn't have any other choice because we narrowed it down to that one issue," said Summers. 

Summers believes no one should have to come out their pockets to be treated fairly. 

"This is not an attempt to turn loose all drunk drivers this is an attempt to require that we have a level playing field in our field of justice." 

On this point, the appeals court also agreed: "Under the scenario suggested by the state, the defendant is forced to obtain an independent test, to pay for an attorney to defend him, and to hire an expensive expert to challenge the [blood alcohol content] result in order to do what an unbiased TBI forensic scientist should have done from the beginning."

Many DUI cases end in guilty pleas. There's a possibility this ruling could impact many of those cases. However, it's not clear if the ruling will be upheld. Prosecutors can appeal this ruling and take the case to the Tennessee Supreme Court.

Here's the entire ruling by the court of criminal appeals:Stay with WRCBtv.com for updates to this story.

PREVIOUS STORY:  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 pecuniary 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.

The Associated Press contributed to this story.