The Supreme Court of Cassation with judgement No. 18507 filed on 21 September 2016, intervened again on the sensitive issue of denial of acceptance of the medical certificate attesting to an employee’s illness. In this case, an employee, unable to work for a declared pathology of acute sciatica, was caught by an investigative agency hired by the employer, to carry out work on the roof and in the courtyard of his own home. According to the judgement under review, the truthfulness of an illness alleged by an employee can be disregarded by the employer “even just by verifying any factual situation – even if not resulting from an health-related investigation – that can demonstrate the absence of illness or its lack of effect in causing inability to work“. The aforementioned judgement also confirms the right of the employer to perform the inspection, even if in secret through an investigator, even in absence of serious suspicions. Therefore, the investigative results, if legitimately acquired, are such as to make the medical certificate issued by affiliated professionals null and void and even if, in general, a medical certificate represents valid evidence until a claim of fraud is brought forth.