In his Supreme Court of Appeal ruling, Judge Lebotsang Bosielo, with four judges concurring, found in favour of a police officer who had been arrested and detained by his colleagues on suspicion of driving under the influence of liquor.
The officer - Johannes Francois Swart - was arrested without a warrant.
Testifying first in the Worcester Magistrate's Court following a civil claim for damages by Swart, constables Jonathan Daniëls and Sonja Nel of De Doorns police station told the court that they arrested Swart after having smelled alcohol in his breath when they confronted him in May 2007.
Daniëls said Swart "reeked" of alcohol while Nel said she "sensed a mild smell of alcohol" on him but could not say whether he was drunk or not.
According to court documents, criminal charges against Swart were withdrawn after blood tests found that his alcohol level "was only 0.04 grams per 100 ml at the time of the incident".
The legal blood alcohol limit in South Africa is 0.05g/100ml.
"He (Daniëls) conceded that he did not perform any tests to determine the respondent's state of sobriety," Bosielo's judgment read.
The magistrate's court dismissed Swart's claim with costs, a decision that was later overturned on appeal by the Western Cape High Court.
Swart was awarded R50,000 in damages as well as interest and costs.
In his affidavit, Constable Daniels said he and Nel were on their way to an accident scene when they came upon Swart.
The officers returned to the scene of Swart's accident where they found his car in a "ditch" about 100metres from where he was standing.
Daniëls then called an officer in charge of the charge office - Inspector Anneke Joubert - who, after having been told by Daniëls that Swart "appeared to be under the influence of alcohol", instructed him to arrest Swart.
In his evidence, Swart conceded that he had spent the night drinking with another police officer after which he got a former informer to drive him home.
The informer, Swart testified, lost control of the car as it veered off the road and later ran away.
In arguing that Swart's arrest was justified, Daniëls had to satisfy the provisions of Section 40(1)(b) of the Criminal Procedure Act 51 of 1977 which states, among others, that "the arresting officer must entertain a suspicion; the suspicion must be that the suspect committed an offence referred to in Schedule 1; and the suspicion must be based on reasonable grounds".
Bosielo found otherwise and said: "Based on the facts, the key question is whether the mere smell of alcohol was sufficient to give rise to a reasonable suspicion on the part of the second appellant (Daniëls) that the respondent (Swart) was under the influence of intoxicating liquor and that for that reason he could not drive a vehicle.
"To my mind, to conclude that the respondent was under the influence of alcohol based on the mere fact that he smelled lightly of alcohol, is more of a quantum leap in logic.
"It follows, in my view, that the second appellant's suspicion was not based on reasonable grounds and therefore that the respondent's arrest and detention were unlawful."