ST. PAUL — The Minnesota Supreme Court has ruled the Intoxilyzer breath test for blood alcohol content is reliable.

The ruling sends more than 4,000 drunken driving cases back to district courts in Minnesota. Defense attorneys have long challenged the reliability of the testing device. In 2006, a Northfield man contested his drunken driving charge, arguing that unless he had access to the device’s computer software, it could not be determined if the Intoxilyzer was working properly.

The Supreme Court agreed Wednesday, noting in its opinion that the validity of the Intoxilyzer could still be challenged if there are problems with the device.