skip to content

Refine results


Search by

Search by Algolia
Law Handbook banner image

Challenging breath test results

Blood tests

Section 47K of the Road Traffic Act 1961 (SA) states that where the police have complied with the requirements relating to breath analysing instruments and procedures, then the concentration of alcohol indicated by the breath analysis instrument as being present in the blood, is presumed to have been present in the blood at the time of analysis and throughout the preceding 3 hours. Prior to 12 December 2022 this time period was 2 hours.

If the breath analysis can be said to have been done more than 3 hours after the driving or attempted driving, then the police cannot rely on the presumption [see for example, Moore v Police (1997) 27 MVR 116; [1997] SASC 6448]).

If a driver wishes to challenge the accuracy of the reading of an alcotest or breath analysis machine taken within 3 hours of their driving or attempted driving, they will have to undergo a blood test. If a blood test is not taken, the result of the breath test cannot be challenged other than in exceptional circumstances (see consuming alcohol after driving).

  • All drivers recording over 0.05 BAC on a breath analysis reading have the right to undergo a blood test.
  • If a reading over 0.05 BAC is recorded, police are obliged to supply written notice of the test reading, the implication of the result and the right to obtain a blood sample. Upon request from the driver, they must also supply a blood test kit.
  • The kit contains a statement of the driver’s right to have a blood test together with instructions to both the driver and a medical practitioner on the procedures that must be followed.
  • Tests must be conducted by a registered medical practitioner or registered nurse.
  • The responsibility for making arrangements to have the blood sample taken lies with the driver. However, if outside metropolitan area and it appears to the police that the person will be unable to travel to a place to have a blood sample taken, the police must provide transport to a suitable place for the blood sample to be taken if requested.
  • The sample is divided into halves with one going to the driver and the other to the police. The police sample will be analysed with the results sent to the driver.
  • A driver may have their sample tested independently if they wish. If this is intended then it is important that the sample be kept in a cool place and analysed as soon as reasonably practicable.
Problems with challenging breath analysis results

A blood test will usually provide a reading lower than that provided by the breath analysis. This is to be expected because it is highly unlikely that the breath analysis and the blood test will be performed within the same hour. Usually a matter of hours will pass before the driver is able to get to a hospital and have a blood sample taken. During this time their blood alcohol level will naturally start to fall, provided they have not been drinking in the interim.

Alcohol elimination rate

When challenging the results of a breath analysis it is necessary to determine the alcohol elimination rate of the person concerned. The alcohol elimination rate measures the rate at which an individual eliminates alcohol from their blood. Alcohol elimination rates vary from person to person but generally between 0.01 to 0.02 gm of alcohol per 100 ml of blood per hour is considered within the normal range, in addition to a 25% margin of error.

Expert medical evidence required

In order to establish that a breath analysis reading was inaccurate, the results of the blood test must be explained and interpreted to the court by a medical expert who can provide evidence about the driver’s alcohol elimination rate at the time of the offence [Tonkin v Police [2006] SASC 145]. This would require further testing through a laboratory at the driver’s expense.

Challenging breath test results  :  Last Revised: Wed May 9th 2007
The content of the Law Handbook is made available as a public service for information purposes only and should not be relied upon as a substitute for legal advice. See Disclaimer for details. For free and confidential legal advice in South Australia call 1300 366 424.