  We study how the stability of spherical crystalline shells under external
pressure is influenced by the defect structure. In particular, we compare
stability for shells with a minimal set of topologically-required defects to
shells with extended defect arrays (grain boundary "scars" with non-vanishing
net disclination charge). We perform Monte Carlo simulations to compare how
shells with and without scars deform quasi-statically under external
hydrostatic pressure. We find that the critical pressure at which shells
collapse is lowered for scarred configurations that break icosahedral symmetry
and raised for scars that preserve icosahedral symmetry. The particular shapes
which arise from breaking of an initial icosahedrally-symmetric shell depend on
the F\"oppl-von K\'arm\'an number.
