Smart v Her Majesty's Advocate 1975 JC 30 is a Scots criminal law case relating to consent as a defence to assault.

The case saw the accused, William Smart, who was charged with assault, lodging the defence that his victim Issac Wilkie has consented to a "square go".

Initially, he asserted that the victim had willingly participated in the fight and comprehended the potential risks, thus challenging the grounds for an assault charge.

Smart chose to appeal this decision claiming consent was a defence to a charge of assault on the grounds that both men had chosen to fight without weapons in similar conditions to a boxing match.

The court held that: "it is in the public interest that it should be decided and made known that consent to a 'square go' is not a defence to a charge of assault based on that agreed combat."