(97) If the processing is carried out by a public authority with the exception of courts or independent judicial authorities in the exercise of justice, or if in the private sector the processing is carried out by a controller whose main activity consists of processing operations that require regular and systematic monitoring of data subjects on a large scale, or if the main activity of the controller or processor consists of large-scale processing of special categories of personal data and personal data relating to criminal convictions and violations of law, the controller or processor should be assisted in monitoring internal compliance with this Regulation by a person with expertise in data protection law and practices. In the private sector, the processing of personal data is the main activity of the controller if it means its core and not side activities. The necessary level of expertise should be determined in particular in light of the data processing operations carried out and the protection required by the personal data processed by the controller or processor. Such data protection officers - whether or not they are employees of the controller - should be able to perform their duties and tasks independently.