The head of the Minnesota Bureau of Criminal Apprehension explained on Monday what caused hundreds of faulty DWI tests.

"There's been a number of human errors that we've identified with these instrumentations," Minnesota BCA Superintendent Drew Evans said. 

The DMT test, which is putting into question hundreds, if not thousands, of DWI cases in the state, is not the standard roadside field sobriety test. It's a secondary breath test administered in jails or police stations.

The machine used for the tests has a bottle that holds gases to ensure the test is calibrated correctly.

Law enforcement, in many cases, has been using the wrong bottle, which can throw off results. So far, the wrong bottle has been used in five counties — Aitkin, Chippewa, Hennepin, Olmsted and Winona — and has compromised 277 cases, and there could be more. That's why all the machines in the state are being checked. 

"They want to make sure they have got the right dry gas bottle, that they are doing it the right way, and so they are going to send a tech to look at everything," defense attorney Dave Risk said.

Risk said that anyone with a DWI can have an attorney check their records and see if the wrong bottle was used. But that won't guarantee getting a guilty verdict overturned. 

"There might be a lot of other evidence. For example, you know, maybe the person couldn't even stand up straight afterwards, needed help getting out of the car," Risk said.

According to Risk, anyone whose DWI case still hasn't gone to court has a better shot of getting it tossed if the wrong bottle was used. 

Right now, officers throughout the state are relying on blood tests in DWI cases. In the future, the BCA will be the only agency calibrating and maintaining the DMT machines.