Michael Servetus was a Spanish physician and theologian whose critique of orthodox Christian doctrines placed him at odds with the contemporary religious leaders, particularly John Calvin, the prominent figure of the Reformation in Geneva. Servetus's most controversial views included his denial of the Trinity, proposing instead a unique interpretation of the biblical texts. This belief directly clashed with Calvinist doctrine and posed a challenge to the theological foundations of the Reformation, leading to increased scrutiny by Calvin and his followers.

Arriving in Geneva, Servetus was initially unaware of the extent of Calvin's influence and the dangers posed to someone of his controversial beliefs. On August 13, 1553, he was arrested, his writings having already drawn the attention of the Calvinist authorities. The trial that ensued was marked by heated discussions about heresy and the limits of acceptable theological discourse. Calvin himself played a critical role in this trial, pushing for Servetus to be condemned for his unorthodox views.

Ultimately, the trial concluded with Servetus found guilty of heresy, reflecting the broader tensions within the Protestant movement concerning freedom of thought and interpretation of scripture. His subsequent execution by burning in October of the same year sent shockwaves through the religious community and initiated discussions on religious tolerance and freedom that would resonate for centuries to follow.