  New data on quasifree polarized neutron-proton scattering, in the region of
the recently observed $d^*$ resonance structure, have been obtained by
exclusive and kinematically complete high-statistics measurements with WASA at
COSY. This paper details the determination of the beam polarization, checks of
the quasifree character of the scattering process, on all obtained $A_y$
angular distributions and on the new partial-wave analysis, which includes the
new data producing a resonance pole in the $^3D_3$-$^3G_3$ coupled partial
waves at ($2380\pm10 - i40\pm5$) MeV -- in accordance with the $d^*$ dibaryon
resonance hypothesis. The effect of the new partial-wave solution on the
description of total and differential cross section data as well as specific
combinations of spin-correlation and spin-transfer observables available from
COSY-ANKE measurements at $T_d$ = 2.27 GeV is discussed.
