  In his 1930 paper, Kuratowksi categorized planar graphs, proving that a
finite graph $\Gamma$ is planar if and only if it does not contain a subgraph
that is homeomorphic to $K_5$, the complete graph on 5 vertices, or $K_{3,3}$,
the complete bipartite graph on six vertices. In their 2001 paper, Davis and
Okun point out that the $K_{3,3}$ graph can be understood as the nerve of a
right-angled Coxeter system and prove that this graph is not planar using
results from $\ell^2$-homology. In this paper, we employ a similar method
proving $K_5$ is not planar.
