What to do when a thief cannot be identified in the workplace

Thieving employees are a huge issue to many businesses across the country, but not for the reason one would expect.
While stealing from an employer is definitely a cause for concern, complications arise because, more often than not, the employer cannot identify the guilty employee. The most sophisticated security measures may be in place, but thieves can be pretty smart too, and can often avoid them.
So what can an employer do in a situation like this? The following case may shed some light on the matter.
CASE LAW:
In the case of  Chauke & Others v Lee Service Centre CC t/a Leeson Motors (1998) 19 ILJ 1441 (LAC) and RSA Geological Services (a division of De Beers Consolidated Mines Ltd) vs Grogan & Others (2008) 2 BLLR 184 (LC) the employer was struggling with theft in the business, but could not identify the perpetrator. There was a strong feeling that other employees knew about it. The employer went ahead and did what any other employer would do in a similar situation – he consulted with the employees to help identify the culprit.
But none of the employees were willing to identify the culprit, even though the employer had sufficient evidence to suggest they did in fact know who was to blame.
What the court then decided was that dismissing the entire group for not helping the employer was justified, because the relationship between employees and employers is ultimately built on trust.
What can be learnt from this case?
If an employer is struggling with theft in the business and have evidence to suggest that employees might know who the culprit is, then they may be dismissed if they refuse to help identify the culprit.