Can covert surveillance be used as evidence when carrying out an investigation?

Covert surveillance often involves an employer monitoring an employee thrush the use of CCTV. The current position adopted by the Data Protection Commissioner (the "DPC"), as published in the recently revised Guidelines on CCTV Usage (the "Guidelines"), is as follows:

1. Covert recording is generally unlawful.
2. Surveillance is normally only permitted on a case by case basis where the data is kept for the purposes of preventing, detecting or investigating offences, or apprehending or prosecuting offenders. The final objective of any recording must be an actual involvement of An Garda Síochána (or other prosecution authorities) for potential criminal investigation or civil legal proceedings