Cape Town - 131002- Arno Carstens arrives at Cape Town magistrates court on drunken driving charges . Picture Brenton Geach

Johannesburg -

Musician Arno Carstens’ trial is expected to resume in the Cape Town Magistrate's Court on Wednesday.

Carstens was arrested three years ago for allegedly driving under the influence of alcohol.

He has pleaded not guilty to a charge of drunk driving, alternatively driving with a blood-alcohol level of 0.20 percent. The legal limit is 0.05 percent.

Before the trial was postponed in February, Carstens' lawyer Milton de la Harpe continued to attack the methodology used by the laboratory which analysed the blood sample.

He also put it to Tim Lourens, the head of forensic toxicology at the University of Pretoria, that blood samples could be deemed unreliable because of the presence of micro-organisms such as bacteria, viruses and fungi.

He said glucose levels presented another possibility for a faulty reading, because glucose was often elevated by shock or stress.

Lourens replied: “If one can inhibit (ethanol) fermentation, then other things can be controlled and reliable.”

When a blood sample was taken from an accused and put into a sterile tube, it was mixed with a sodium fluoride powder to prevent the formation of such micro-organisms. - Sapa