Recent high profile cases like Wisheart (Bristol babies) has placed healthcare professional autonomy under both ethical and legal scrutiny, reflected by the growing number of civil cases brought by the public. The aim of this paper is to investigate the effect of evidence-based treatment on the legal requirements of consent, when the treatment transcends the therapeutic boundary. The potential effect on the autonomy of healthcare professionals is also discussed. The study revealed that although consent remains the cornerstone of defence in many areas of therapeutic treatment, it is open to significant legal challenge in the grey area between therapeutic evidence-based treatment and non-evidenced-based procedures. Consent remains the cornerstone of defence for therapeutic procedures. However, it is less certain with innovative treatment or procedures that transcend the therapeutic boundaries and are shown to be non-evidence-based.