What was the 1954 US Supreme Court case Gibbons v Wright about?

The 1954 Gibbons versus Wright case was tried by the Australian Supreme Court, not the US Supreme Court. The case was a familial dispute, in which Gibbons believed her sisters in law were mentally incompetent, thus rendering the paperwork they had drawn up on a shared parcel of land void. The justices ruled in favor of the sisters in law, declaring that they only needed to be mentally sound enough to understand the contracts they were signing.