  Although commonly assumed to be spherical, dark matter halos are predicted to
be non-spherical by N-body simulations and their asphericity has a potential
impact on the systematic uncertainties in dark matter searches. The evaluation
of these uncertainties is the main aim of this work, where we study the impact
of aspherical dark matter density distributions in Milky-Way-like halos on
direct and indirect searches. Using data from the large N-body cosmological
simulation Bolshoi, we perform a statistical analysis and quantify the
systematic uncertainties on the determination of local dark matter density and
the so-called $J$ factors for dark matter annihilations and decays from the
galactic center. We find that, due to our ignorance about the extent of the
non-sphericity of the Milky Way dark matter halo, systematic uncertainties can
be as large as 35%, within the 95% most probable region, for a spherically
averaged value for the local density of 0.3-0.4 GeV/cm$^3$. Similarly,
systematic uncertainties on the $J$ factors evaluated around the galactic
center can be as large as 10% and 15%, within the 95% most probable region, for
dark matter annihilations and decays, respectively.
