Kerala High Court mandates air blank test with ‘0.000’ reading before breathalyser use for drunken driving cases

While stating that an ‘air blank test’ is conducted and a reading of ‘0.000’ is displayed on the device before subjecting a person to a breathalyser test for drunken driving, the Kerala High Court has directed the Director General of Police to issue directions in this regard to the police officers concerned.

The primary goal of a blank test is to verify whether the breath-alcohol testing device is functioning correctly and is not influenced by any residual alcohol from previous tests. Therefore, it is mandatory to conduct an air blank test and ensure that the calibration is at ‘zero’ before taking a new breath sample, Justice V.G. Arun said, while quashing a case against Saran Kumar S., a two-wheeler rider from Thiruvananthapuram.

The police had charged him with driving his vehicle on the Medical College-Kumarapuram Road in a rash and negligent manner in December 2024. Based on the suspicion that Mr. Kumar, the petitioner in this case, had consumed alcohol, he was arrested and later released on self-bond after conducting a breathalyser test.

His counsel contended that the printout of the test showed the reading in the blank test conducted, immediately before the his breath sample was taken, as 412 mg/100 ml. The police were bound to ensure that the calibration of the device showed ‘zero’ before conducting the breathalyser test.

The court said the primary goal of a blank test is to verify that the breathalyser device is functioning correctly and is not influenced by any residual alcohol from previous tests. As the petitioner was not subjected to a separate medical test, there is no acceptable evidence regarding the alcohol level in his blood. In such circumstances, prosecution for the offence of driving under the influence of alcohol or drugs will be an exercise in futility, it added.