In 1843, Daniel M’Naghten gunned down another man in broad daylight. But when he was taken to trial things got complicated. His defense argued that he shouldn’t be held fully responsible because he wasn’t in his right mind. However, the courts didn’t know what to do with that because there was no precedent for this kind of thing. So his defense team got to work putting in place a defense strategy that is still used, almost in the exact same way, almost 200 years later.